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/ARCMigrate/TransRetainReleaseDealloc.cpp b/clang/lib/ARCMigrate/TransRetainReleaseDealloc.cpp
index 389f3655..ebe289b 100644
--- a/clang/lib/ARCMigrate/TransRetainReleaseDealloc.cpp
+++ b/clang/lib/ARCMigrate/TransRetainReleaseDealloc.cpp
@@ -158,7 +158,7 @@
   }
 
 private:
-  /// \brief Checks for idioms where an unused -autorelease is common.
+  /// Checks for idioms where an unused -autorelease is common.
   ///
   /// Returns true for this idiom which is common in property
   /// setters:
@@ -309,7 +309,7 @@
     return nullptr;
   }
 
-  /// \brief Check if the retain/release is due to a GCD/XPC macro that are
+  /// Check if the retain/release is due to a GCD/XPC macro that are
   /// defined as:
   ///
   /// #define dispatch_retain(object) ({ dispatch_object_t _o = (object); _dispatch_object_validate(_o); (void)[_o retain]; })