ext/readline: Fix flacky readline CLI pager test

This fix the ext/readline/tests/readline_cli_pager.phpt test
introduced in GH-22994.

Author: LamentXU123

ext/readline/readline_cli.c

@@ -710,7 +710,7 @@ static int readline_shell_run(void) /* {{{ */
 		}
 
 		if (pager_pipe) {
-			fclose(pager_pipe);
+			pclose(pager_pipe);
 			pager_pipe = NULL;
 		}