component file sharing: fix method name case:

`render_OPTIONS` is a method inherited from Twisted, name has been put to lowercase
following massive refactoring, resulting in the method not being called anymore. This
patch fixes it.

libervia/backend/plugins/plugin_comp_file_sharing.py

@@ -136,7 +136,7 @@ class HTTPFileServer(resource.Resource):
             "Date, Content-Length, Content-Range")
         return super().render(request)
 
-    def render_options(self, request):
+    def render_OPTIONS(self, request):
         request.setResponseCode(http.OK)
         return b""