status: close file descriptor after reading git-rebase-todo

Reported via Coverity.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

wt-status.c

@@ -1155,6 +1155,7 @@ static int read_rebase_todolist(const char *fname, struct string_list *lines)
 		abbrev_sha1_in_line(&line);
 		string_list_append(lines, line.buf);
 	}
+	fclose(f);
 	return 0;
 }