Remove \brief commands from doxygen comments.

This is similar to the LLVM change https://reviews.llvm.org/D46290.

We've been running doxygen with the autobrief option for a couple of
years now. This makes the \brief markers into our comments
redundant. Since they are a visual distraction and we don't want to
encourage more \brief markers in new code either, this patch removes
them all.

Patch produced by

for i in $(git grep -l '\@brief'); do perl -pi -e 's/\@brief //g' $i & done
for i in $(git grep -l '\\brief'); do perl -pi -e 's/\\brief //g' $i & done

Differential Revision: https://reviews.llvm.org/D46320

llvm-svn: 331834
diff --git a/clang/lib/Sema/SemaCoroutine.cpp b/clang/lib/Sema/SemaCoroutine.cpp
index 36d5523..aefea98 100644
--- a/clang/lib/Sema/SemaCoroutine.cpp
+++ b/clang/lib/Sema/SemaCoroutine.cpp
@@ -1438,7 +1438,7 @@
       .get();
 }
 
-/// \brief Build a variable declaration for move parameter.
+/// Build a variable declaration for move parameter.
 static VarDecl *buildVarDecl(Sema &S, SourceLocation Loc, QualType Type,
                              IdentifierInfo *II) {
   TypeSourceInfo *TInfo = S.Context.getTrivialTypeSourceInfo(Type, Loc);