screenshot-window-sizer: Do not translate schema for now

It's not worth a string freeze break, we can revert after the freeze
has been lifted ...

extensions/screenshot-window-sizer/org.gnome.shell.extensions.screenshot-window-sizer.gschema.xml.in

@@ -4,7 +4,7 @@
           path="/org/gnome/shell/extensions/screenshot-window-sizer/">
     <key type="as" name="cycle-screenshot-sizes">
       <default><![CDATA[['<Alt><Control>s']]]></default>
-      <_summary>Cycle Screenshot Sizes</_summary>
+      <summary>Cycle Screenshot Sizes</summary>
     </key>
   </schema>
 </schemalist>

po/POTFILES.in

@@ -15,7 +15,6 @@ extensions/native-window-placement/extension.js
 extensions/native-window-placement/org.gnome.shell.extensions.native-window-placement.gschema.xml.in
 extensions/places-menu/extension.js
 extensions/places-menu/placeDisplay.js
-extensions/screenshot-window-sizer/org.gnome.shell.extensions.screenshot-window-sizer.gschema.xml.in
 extensions/systemMonitor/extension.js
 extensions/user-theme/extension.js
 extensions/user-theme/org.gnome.shell.extensions.user-theme.gschema.xml.in