Bug 1465323 - Update FxAccountUpgradeReceiver. r=JanH

Listening for `ACTION_MY_PACKAGE_REPLACED` [1] is the easiest way to get notified
when the app has been updated.
This broadcast, while not explicitly exempt from Oreo's Background Execution
Limits [2] is considered explicit because it is sent only to the package being
replaced and so it is compatible with the new limitations.

The previous intent action was chosen because at that time this action was not
supported by all platforms Fennec ran on [3], but this is not the case anymore.

[1] https://developer.android.com/reference/android/content/Intent.html#ACTION_MY_PACKAGE_REPLACED
[2] https://developer.android.com/guide/components/broadcast-exceptions
[3] 5c06063be6

MozReview-Commit-ID: Ak0dd2koJ9U

--HG--
extra : rebase_source : 58f32f574b13e5d7e9256f578821445eae1e3b57
extra : histedit_source : 204d858fe7408276714b2d228b612baddf76804d

mobile/android/services/manifests/FxAccountAndroidManifest_activities.xml.in

@@ -21,8 +21,7 @@
         <receiver
             android:name="org.mozilla.gecko.fxa.receivers.FxAccountUpgradeReceiver">
             <intent-filter>
-                <action android:name="android.intent.action.PACKAGE_REPLACED" />
-                <data android:scheme="package"/>
+                <action android:name="android.intent.action.MY_PACKAGE_REPLACED" />
             </intent-filter>
         </receiver>