MimeDatabase: Remove bestMatch, which was broken beyond repair

The problem is that, if you check e.g. a .pro file against all C/C++ mime
types, and these define magic matchers, it would find that .pro doesn't
match C/C++ mime types by extension, so it would open the file to find a
magic match. Even though the extension .pro would identify it already as
a qmake .pro file when checking for the mime type globally.

Change-Id: I3341187e88e2263bf38169c3c99e5d2161e2a9ee
Reviewed-by: Daniel Teske <daniel.teske@theqtcompany.com>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/cpptools/cppprojectfile.h

@@ -88,7 +88,6 @@ private:
 
     QList<ProjectFile> &m_files;
     QHash<QString, ProjectFile::Kind> m_mimeNameMapping;
-    QList<Utils::MimeType> m_mimeTypes;
 };
 
 } // namespace Internal