keyboard: Fix check for existing shortcut settings

From a Coverity scan:

panels/keyboard/cc-keyboard-manager.c:208: unreachable: Since the loop
increment "i++;" is unreachable, the loop body will never execute more
than once.

This seems like a logic thinko introduced in commit
3207fe97ec . In practice it was unlikely
to be a problem since we don't have repeated shortcut gsettings key
names in all our KeyListEntries files.

panels/keyboard/cc-keyboard-manager.c

@@ -214,8 +214,6 @@ have_key_for_group (CcKeyboardManager *self,
             {
               return TRUE;
             }
-
-          return FALSE;
         }
     }