[libc++] Update clang-format style.

After evaluating the new style I noticed inner namespaces are now
indented. I am not fond of that style and I've seen some other review
comment in this regard so I propose we remove this option and use the
LLVM default not to indent it.

Reviewed By: ldionne, philnik, var-const, #libc

Differential Revision: https://reviews.llvm.org/D129441

libcxx/.clang-format

@@ -65,10 +65,9 @@ IndentRequires: true
 InsertTrailingCommas: Wrapped
 KeepEmptyLinesAtTheStartOfBlocks: false
 MaxEmptyLinesToKeep: 1
-NamespaceIndentation: Inner
 PackConstructorInitializers: NextLine
 
-PenaltyIndentedWhitespace: 61
+PenaltyIndentedWhitespace: 2
 
 Language: Cpp
 Standard: c++20