Marking Surtr referenced rules RSharedStrings, RemoteStrings, and GmRemoteStrings as private to limit false alerts.

RSharedStrings alerts on Microsoft signed wininet.dll	6B39A43271B0A631EAEFDAFDD51D17E3
SharedStrings alerts on Microsoft signed ntoskrnl.exe 68762D4C4412B4BB52BE2FC11F977503

Signed-off-by: Ryan B <randomrhythm@rhythmengineering.com>