doc: mark --jitless as experimental

It's already documented as such, but it doesn't have the label.

PR-URL: #51247
Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Reviewed-By: Akhil Marsonya <akhil.marsonya27@gmail.com>

doc/api/cli.md

@@ -1259,13 +1259,13 @@ Opens the REPL even if stdin does not appear to be a terminal.
 added: v12.0.0
 -->
 
+> Stability: 1 - Experimental. This flag is inherited from V8 and is subject to
+> change upstream.
+
 Disable [runtime allocation of executable memory][jitless]. This may be
 required on some platforms for security reasons. It can also reduce attack
 surface on other platforms, but the performance impact may be severe.
 
-This flag is inherited from V8 and is subject to change upstream. It may
-disappear in a non-semver-major release.
-
 ### `--max-http-header-size=size`
 
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