Fix pg_regress arg parsing error

Due to a option index error, exclude-tests, ignore-plans, prehook and
print-failure-diffs are not parsed from command line correctly.

src/test/regress/pg_regress.c

@@ -2625,10 +2625,10 @@ regression_main(int argc, char *argv[], init_function ifunc, test_function tfunc
 		{"load-extension", required_argument, NULL, 22},
 		{"config-auth", required_argument, NULL, 24},
 		{"init-file", required_argument, NULL, 25},
-		{"exclude-tests", required_argument, NULL, 27},
-		{"ignore-plans", no_argument, NULL, 28},
-		{"prehook", required_argument, NULL, 29},
-		{"print-failure-diffs", no_argument, NULL, 30},
+		{"exclude-tests", required_argument, NULL, 26},
+		{"ignore-plans", no_argument, NULL, 27},
+		{"prehook", required_argument, NULL, 28},
+		{"print-failure-diffs", no_argument, NULL, 29},
 		{"tablespace-dir", required_argument, NULL, 80},
 		{NULL, 0, NULL, 0}
 	};