No issue: Use 'Turn on Sync' instead of 'Sign In'

Seems like we've started using a wrong string at some point.
Thankfully, the correct one is already in the tree.

app/src/main/res/xml/preferences.xml

@@ -11,7 +11,7 @@
         android:key="@string/pref_key_sign_in"
         android:layout="@layout/sign_in_preference"
         android:summary="@string/preferences_sign_in_description"
-        android:title="@string/preferences_sign_in" />
+        android:title="@string/preferences_sync" />
 
     <androidx.preference.PreferenceCategory
         android:key="@string/pref_key_account_category"

app/src/main/res/xml/turn_on_sync_preferences.xml

@@ -11,7 +11,7 @@
         android:icon="@drawable/ic_qr" />
     <androidx.preference.Preference
         android:key="@string/pref_key_sync_sign_in"
-        android:title="@string/preferences_sync_sign_in"
+        android:title="@string/preferences_sync"
         android:icon="@drawable/ic_sign_in" />
     <androidx.preference.Preference
         android:key="@string/pref_key_sync_create_account"