[App] Remove unused string. Leftover from alternate implementation.

Author: ViliusSutkus89

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

@@ -13,7 +13,6 @@
     <string name="conversion_status_error">Conversion failed!</string>
     <string name="conversion_status_input">Copying PDF file to cache …</string>
     <string name="conversion_status_work">Converting PDF to HTML …</string>
-    <string name="conversion_status_output">Loading HTML file …</string>
 
     <string name="button_cancel">Cancel</string>