Remove "reference" as directive keyword

src/Compilers/VisualBasic/Portable/Syntax/SyntaxKindFacts.vb

@@ -799,7 +799,6 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
                    {"out", SyntaxKind.OutKeyword},
                    {"preserve", SyntaxKind.PreserveKeyword},
                    {"region", SyntaxKind.RegionKeyword},
-                   {"reference", SyntaxKind.ReferenceKeyword},
                    {"r", SyntaxKind.ReferenceKeyword},
                    {"skip", SyntaxKind.SkipKeyword},
                    {"strict", SyntaxKind.StrictKeyword},
@@ -835,7 +834,6 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
                    {"const", SyntaxKind.ConstKeyword},
                    {"externalsource", SyntaxKind.ExternalSourceKeyword},
                    {"externalchecksum", SyntaxKind.ExternalChecksumKeyword},
-                   {"reference", SyntaxKind.ReferenceKeyword},
                    {"r", SyntaxKind.ReferenceKeyword},
                    {"enable", SyntaxKind.EnableKeyword},
                    {"disable", SyntaxKind.DisableKeyword}

src/Compilers/VisualBasic/Portable/VBResources.Designer.vb

@@ -3783,7 +3783,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
         End Property
         
         '''<summary>
-        '''  Looks up a localized string similar to &apos;If&apos;, &apos;ElseIf&apos;, &apos;Else&apos;, &apos;Const&apos;, &apos;Region&apos;, &apos;ExternalSource&apos;, &apos;ExternalChecksum&apos;, &apos;Enable&apos;, &apos;Disable&apos;, &apos;End&apos;, &apos;R&apos;, or &apos;Reference&apos; expected..
+        '''  Looks up a localized string similar to &apos;If&apos;, &apos;ElseIf&apos;, &apos;Else&apos;, &apos;Const&apos;, &apos;Region&apos;, &apos;ExternalSource&apos;, &apos;ExternalChecksum&apos;, &apos;Enable&apos;, &apos;Disable&apos;, &apos;End&apos; or &apos;R&apos; expected..
         '''</summary>
         Friend ReadOnly Property ERR_ExpectedConditionalDirective() As String
             Get

src/Compilers/VisualBasic/Portable/VBResources.resx

@@ -742,7 +742,7 @@
     <value>'{0}' is not valid on a local variable declaration.</value>
   </data>
   <data name="ERR_ExpectedConditionalDirective" xml:space="preserve">
-    <value>'If', 'ElseIf', 'Else', 'Const', 'Region', 'ExternalSource', 'ExternalChecksum', 'Enable', 'Disable', 'End', 'R', or 'Reference' expected.</value>
+    <value>'If', 'ElseIf', 'Else', 'Const', 'Region', 'ExternalSource', 'ExternalChecksum', 'Enable', 'Disable', 'End' or 'R' expected.</value>
   </data>
   <data name="ERR_ExpectedEQ" xml:space="preserve">
     <value>'=' expected.</value>
@@ -5338,4 +5338,4 @@
   <data name="ERR_InvalidPathMap" xml:space="preserve">
     <value>The pathmap option was incorrectly formatted.</value>
   </data>
-</root>
+</root>
\ No newline at end of file

src/Compilers/VisualBasic/Test/Syntax/Syntax/SyntaxFactsTest.vb

@@ -102,7 +102,7 @@ Public Class SyntaxFactsTests
         Assert.Equal(SyntaxKind.None, SyntaxFacts.GetContextualKeywordKind(String.Empty))
         Assert.Equal(SyntaxKind.None, SyntaxFacts.GetBaseTypeStatementKind(SyntaxKind.ForKeyword))
 
-        Dim expected = New String() {"aggregate", "all", "ansi", "ascending", "assembly", "async", "auto", "await", "binary", "by", "compare", "custom", "descending", "distinct", "equals", "explicit", "externalsource", "externalchecksum", "from", "group", "infer", "into", "isfalse", "istrue", "iterator", "join", "key", "mid", "off", "order", "out", "preserve", "region", "skip", "strict", "take", "text", "unicode", "until", "where", "type", "xml", "yield", "enable", "disable", "warning", "reference"}
+        Dim expected = New String() {"aggregate", "all", "ansi", "ascending", "assembly", "async", "auto", "await", "binary", "by", "compare", "custom", "descending", "distinct", "equals", "explicit", "externalsource", "externalchecksum", "from", "group", "infer", "into", "isfalse", "istrue", "iterator", "join", "key", "mid", "off", "order", "out", "preserve", "r", "region", "skip", "strict", "take", "text", "unicode", "until", "where", "type", "xml", "yield", "enable", "disable", "warning"}
         For Each item In expected
             Assert.NotEqual(SyntaxKind.None, SyntaxFacts.GetContextualKeywordKind(item))
         Next