Remove `IsEmpty` workaround in `Span` and `ReadOnlySpan` (#66865)

* Revert "Workaround to remove unnecessary bounds checks when using {ReadOnly}Span.IsEmpty (dotnet/coreclr#19640)"

This reverts commit 82bd67f7.

* Update doc comments

* Apply suggestions from code review
Co-authored-by: NRobin Lindner <robin.lindner1@t-online.de>

* Apply suggestions from code review
Co-authored-by: NRobin Lindner <robin@deeprobin.de>
Co-authored-by: NAaron Robinson <arobins@microsoft.com>
Co-authored-by: NRobin Lindner <robin.lindner1@t-online.de>
Co-authored-by: NRobin Lindner <robin@deeprobin.de>

src/libraries/System.Private.CoreLib/src/System/ReadOnlySpan.cs

@@ -147,12 +147,13 @@ public int Length
         }
 
         /// <summary>
-        /// Returns true if Length is 0.
+        /// Gets a value indicating whether this <see cref="ReadOnlySpan{T}"/> is empty.
         /// </summary>
+        /// <value><see langword="true"/> if this span is empty; otherwise, <see langword="false"/>.</value>
         public bool IsEmpty
         {
             [NonVersionable]
-            get => 0 >= (uint)_length; // Workaround for https://github.com/dotnet/runtime/issues/10950
+            get => _length == 0;
         }
 
         /// <summary>

src/libraries/System.Private.CoreLib/src/System/Span.cs

@@ -152,12 +152,13 @@ public int Length
         }
 
         /// <summary>
-        /// Returns true if Length is 0.
+        /// Gets a value indicating whether this <see cref="Span{T}"/> is empty.
         /// </summary>
+        /// <value><see langword="true"/> if this span is empty; otherwise, <see langword="false"/>.</value>
         public bool IsEmpty
         {
             [NonVersionable]
-            get => 0 >= (uint)_length; // Workaround for https://github.com/dotnet/runtime/issues/10950
+            get => _length == 0;
         }
 
         /// <summary>