Make RestartForInternalBufferSize static on Linux as required by CA1822.

Author: tmds

src/libraries/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.Linux.cs

@@ -97,7 +97,7 @@ private void FinalizeDispose()
 
         private INotify.Watcher? _watcher;
 
-        private void RestartForInternalBufferSize()
+        private static void RestartForInternalBufferSize()
         {
             // The implementation is not using InternalBufferSize. There's no need to restart.
         }