chore(pushbox): remove statsd metric tags

Because:
 - the statsd metric tags for pushbox are unnecessarily wasteful

This commit:
 - remove the tags

packages/fxa-auth-server/lib/pushbox/index.ts

@@ -176,11 +176,7 @@ export const pushboxApi = (
             'pushbox.db.retrieve.success',
             performance.now() - startTime
           );
-          statsd.increment('pushbox.db.retrieve', {
-            uid,
-            deviceId,
-            msgCount: result.messages.length.toString(),
-          });
+          statsd.increment('pushbox.db.retrieve');
           return {
             last: result.last,
             index: result.index,
@@ -254,7 +250,7 @@ export const pushboxApi = (
             'pushbox.db.store.success',
             performance.now() - startTime
           );
-          statsd.increment('pushbox.db.store', { uid, deviceId });
+          statsd.increment('pushbox.db.store');
           return { index: result.idx };
         } catch (err) {
           statsd.timing(

packages/fxa-auth-server/test/local/pushbox.js

@@ -97,8 +97,7 @@ describe('pushbox', () => {
           );
           sinon.assert.calledOnceWithExactly(
             mockStatsD.increment,
-            'pushbox.db.store',
-            { uid: mockUid, deviceId: mockDeviceIds[0] }
+            'pushbox.db.store'
           );
           assert.equal(index, '12');
         });