Fixed/added namespace ending comments using clang-tidy. NFC

The patch is generated using this command:

tools/clang/tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \
  -checks=-*,llvm-namespace-comment -header-filter='llvm/.*|clang/.*' \
  llvm/lib/


Thanks to Eugene Kosov for the original patch!

llvm-svn: 240137
diff --git a/llvm/lib/MC/MCWinEH.cpp b/llvm/lib/MC/MCWinEH.cpp
index d5d9ead..9cf2edf 100644
--- a/llvm/lib/MC/MCWinEH.cpp
+++ b/llvm/lib/MC/MCWinEH.cpp
@@ -74,6 +74,6 @@
   return getUnwindInfoSection(".xdata", XData, Function, Context);
 }
 
-}
-}
+} // namespace WinEH
+} // namespace llvm