mozilla#186: Enable price polling in certain privacy contexts

Previously, price polling (a.k.a. background price updates) was disabled when Do Not Track, Tracking Protection or certain cookie settings ('reject_third_party' and 'reject_all') were enabled.

Now, price polling occurs in these situations. This leaves the `shouldUpdatePrices` function in `privacy.js` kind of useless, but I left it there instead of removing it entirely in order to add the Private Browsing check that is part of mozilla#177.

src/privacy.js

@@ -44,18 +44,7 @@ export async function shouldCollectTelemetry(method) {
  * @return {boolean}
  */
 export async function shouldUpdatePrices() {
-  if (await trackingProtectionEnabled()) {
-    return false;
-  }
-
-  if (doNotTrackEnabled()) {
-    return false;
-  }
-
-  if (await cookiesBlocked()) {
-    return false;
-  }
-
+  // TODO (bdanforth): Add private browsing check per #177
   return true;
 }