Delete completion scripts during removal

Author: jc00ke

Makefile

@@ -65,5 +65,6 @@ install:
 uninstall:
 	for file in $(INSTALL_FILES); do rm -f $(DESTDIR)$(PREFIX)/$$file; done
 	rm -rf $(DESTDIR)$(DOC_DIR)
+	rm $(COMPLETION_DIR)/$(NAME)
 
 .PHONY: build man update download sign verify clean check test tag release rpm install uninstall all