test_escape: Fix output of --help

The short option name -f was not listed, only its long option name
--force-unsupported.

Author: Japin Li
Discussion: https://postgr.es/m/ME0P300MB04452BD1FB1B277D4C1C20B9B6C52@ME0P300MB0445.AUSP300.PROD.OUTLOOK.COM
Backpatch-through: 13

src/test/modules/test_escape/test_escape.c

@@ -801,7 +801,7 @@ usage(const char *hint)
 		   "  -c, --conninfo=CONNINFO   connection information to use\n"
 		   "  -v, --verbose             show test details even for successes\n"
 		   "  -q, --quiet               only show failures\n"
-		   "      --force-unsupported   test invalid input even if unsupported\n"
+		   "  -f, --force-unsupported   test invalid input even if unsupported\n"
 		);
 
 	if (hint)