Use the real CXXScopeSpec when setting the correction SourceRange.

Otherwise, in the most important case and the only case where SS and
TempSS are different (which is when the CXXScopeSpec should be dropped,
and TempSS is NULL) the wrong SourceRange will be used in the fixit for
the typo correction. Fixes the remaining issue in PR20626.

llvm-svn: 227278