[skip ci] Document --repeat flag as internal (phpGH-16698)

Co-authored-by: Christoph M. Becker <cmbecker69@gmx.de>

Author: iluuu1994

sapi/cli/php_cli.c

@@ -507,6 +507,9 @@ static void php_cli_usage(char *argv0)
 				"  --rz <name>      Show information about Zend extension <name>.\n"
 				"  --ri <name>      Show configuration for extension <name>.\n"
 				"\n"
+				"  --repeat <count> Repeat script execution <count> times.\n"
+				"                   For internal purposes only.\n"
+				"\n"
 				, prog, prog, prog, prog, prog, prog, prog);
 }
 /* }}} */