remove a log message about fetching URLs (#643)

Every fetch made from the client is logged to the console.
But this isn't really necessary, and is particularly confusing
in grist-static, where those fetches are virtualized.

Tests in grist-saas may need adjusting to remove the logger.

test/server/lib/helpers/TestServer.ts

@@ -137,7 +137,6 @@ export class TestServer {
       headers: {Authorization: `Bearer api_key_for_${user}`},
       fetch: fetch as unknown as typeof globalThis.fetch,
       newFormData: () => new FormData() as any,
-      logger: log
     });
   }