Update action_display_cover_only_grid string

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

@@ -91,7 +91,7 @@
     <string name="action_display_grid">Compact grid</string>
     <string name="action_display_comfortable_grid">Comfortable grid</string>
     <string name="action_display_list">List</string>
-    <string name="action_display_cover_only_grid">Cover only grid</string>
+    <string name="action_display_cover_only_grid">Cover-only grid</string>
     <string name="action_display_download_badge">Downloaded chapters</string>
     <string name="action_display_unread_badge">Unread chapters</string>
     <string name="action_display_local_badge">Local manga</string>