Fix the build
Fix the build

Add SuppressMessage attribute for unused field GuidList.guidContextMenuSet.

This field breaks build of GitHub.VisualStudio project with error:

    >  Running Code Analysis...
    >MSBUILD : error CA1823: Microsoft.Performance : It appears that field 'GuidList.guidContextMenuSet' is never used or is only ever assigned to. Use this field or remove it.
    >  Code Analysis Complete -- 1 error(s), 0 warning(s)

This field is already used in another branch (PR https://github.com/github/VisualStudio/pull/156).

github/VisualStudio,github/VisualStudio,github/VisualStudio,HeadhunterXamd/VisualStudio