Fix awkward phrasing in backup dialog

backupdlg.ui

@@ -328,7 +328,7 @@ p, li { white-space: pre-wrap; }
     <item>
      <widget class="QCheckBox" name="showFileDialog">
       <property name="text">
-       <string>When finished, open file selection dialog to allow me unmount the disk</string>
+       <string>When finished, open file selection dialog to allow me to unmount the disk</string>
       </property>
      </widget>
     </item>

restoredlg.ui

@@ -255,7 +255,7 @@ p, li { white-space: pre-wrap; }
     <item>
      <widget class="QCheckBox" name="showFileDialog">
       <property name="text">
-       <string>When finished, open file selection dialog to allow me unmount the disk</string>
+       <string>When finished, open file selection dialog to allow me to unmount the disk</string>
       </property>
      </widget>
     </item>