Remove unneeded redeclaration of reference_wrapper.

llvm-svn: 232887
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: ec6c06610fe41ee78261efc06ea86a8e87af12ed
1 file changed