Revert "CPP: Workaround improvement for File.compiledAsMicrosoft."

This reverts commit c3ec7b5.

Author: geoffw0

cpp/ql/src/semmle/code/cpp/File.qll

@@ -309,10 +309,6 @@ class File extends Container, @file {
     ) or exists(File parent |
       parent.compiledAsMicrosoft() and
       parent.getAnIncludedFile() = this
-    ) or (
-      getAbsolutePath().charAt(1) = ":"
-      	// this is not ideal, it detects compilation on a Windows file system
-      	// as a heuristic approximation to compilation with a Microsoft compiler.
     )
   }