[fenix] For https://github.com/mozilla-mobile/fenix/issues/1573 - Update collections button string

app/src/main/res/layout/save_tab_group_button.xml

@@ -28,6 +28,6 @@
         android:focusable="false"
         android:gravity="center"
         android:textStyle="bold"
-        android:text="@string/save_tab_group"
+        android:text="@string/save_to_collection"
         android:textColor="?contrastText"/>
 </FrameLayout>

app/src/main/res/values/strings.xml

@@ -247,8 +247,8 @@
     <string name="current_session_share">Share</string>
     <!-- Content description (not visible, for screen readers etc.): Title icon for current session menu -->
     <string name="current_session_image">Current session image</string>
-    <!-- Button to save the current set of tabs into a group -->
-    <string name="save_tab_group">Save Tab Group</string>
+    <!-- Button to save the current set of tabs into a collection -->
+    <string name="save_to_collection">Save to collection</string>
     <!-- Text for the button to delete a session -->
     <string name="session_delete">Delete session</string>
     <!-- Text for the button to delete a single session -->