Removing some more unnecessary manual quotes from attribute diagnostics.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198391 91177308-0d34-0410-b5e6-96231b3b80d8
Removing some more unnecessary manual quotes from attribute diagnostics.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198392 91177308-0d34-0410-b5e6-96231b3b80d8
Removing some more unnecessary manual quotes from diagnostics.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198395 91177308-0d34-0410-b5e6-96231b3b80d8