Remove storage permission requirement

It's no longer necessary for importing/exporting blocked numbers.

Context:
 - FossifyOrg/commons#82
 - https://github.com/FossifyOrg/Messages/discussions/309

Author: naveensingh

app/src/main/AndroidManifest.xml

@@ -22,10 +22,6 @@
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
     <uses-permission android:name="android.permission.READ_SYNC_SETTINGS" />
 
-    <uses-permission
-        android:name="android.permission.WRITE_EXTERNAL_STORAGE"
-        android:maxSdkVersion="28" />
-
     <uses-permission
         android:name="android.permission.USE_FINGERPRINT"
         tools:node="remove" />