clang-format: don't indent namespaces

This change doesn't affect existing code. Inner namespace indentation
can lead to a lot of indentation in the case of anonymous namespaces and
the like, impeding readability. Of the clang-format builtin styles
LLVM, Google, Chromium and Mozilla use None while WebKit uses Inner.
Signed-off-by: NIan Rogers <irogers@google.com>
Signed-off-by: NMiguel Ojeda <miguel.ojeda.sandonis@gmail.com>

.clang-format

@@ -482,7 +482,7 @@ KeepEmptyLinesAtTheStartOfBlocks: false
 MacroBlockBegin: ''
 MacroBlockEnd: ''
 MaxEmptyLinesToKeep: 1
-NamespaceIndentation: Inner
+NamespaceIndentation: None
 #ObjCBinPackProtocolList: Auto # Unknown to clang-format-5.0
 ObjCBlockIndentWidth: 8
 ObjCSpaceAfterProperty: true