[clang-format] C# formatting a class with inheritance followed by an attribute...

[clang-format] C# formatting a class with inheritance followed by an attribute specifier assume its a braces initializer

Summary:
https://bugs.llvm.org/show_bug.cgi?id=44340

The rule that prevents `... {} [[....]]`  being treated as a braced initializer for C++ causes problems for C# with attributes, causing it to be incorrectly classified and then messing up the subsequent formatting. (see bug for details of formatting)

Reviewers: mitchell-stellar, klimek, sammccall

Reviewed By: mitchell-stellar

Subscribers: cfe-commits

Tags: #clang-format, #clang

Differential Revision: https://reviews.llvm.org/D71769