Revert "ToolingTest.cpp: Fix r158592, runToolOnCode.FindsNoTopLevelDeclOnEmptyCode on msvc. LangOpts.MicrosoftExt still appends "class type_info;"."

type_info has been made an implicitly predeclared type in r198497 and will no
longer appear as a user-declared type so we can remove this old hack.

This reverts commit r158595.