[ClangTidy] Separate tests for infrastructure and checkers, fixup

Renamed a file that I missed in r374540.

llvm-svn: 374549

diff --git a/clang-tools-extra/test/clang-tidy/infrastructure/Inputs/Headers/stdio.h b/clang-tools-extra/test/clang-tidy/checkers/Inputs/Headers/stdio.h
similarity index 100%
rename from clang-tools-extra/test/clang-tidy/infrastructure/Inputs/Headers/stdio.h
rename to clang-tools-extra/test/clang-tidy/checkers/Inputs/Headers/stdio.h