minor #1662 Remove experimental tag to HTML syntax (WebMamba)

This PR was merged into the 2.x branch.

Discussion
----------

Remove experimental tag to HTML syntax

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| Issues        | Fix #
| License       | MIT

What do you think? Pretty stable now?

Commits
-------

4856f89 Remove experimental tag to HTML syntax

Author: kbond

src/TwigComponent/doc/index.rst

@@ -274,10 +274,6 @@ namespace. See :ref:`Configuration <configuration>`.
 Component HTML Syntax
 ~~~~~~~~~~~~~~~~~~~~~
 
-.. versionadded:: 2.8
-
-    This syntax was been introduced in 2.8 and is still experimental.
-
 So far so good! To make it *really* nice to work with Twig Components, it
 comes with an HTML-like syntax where props are passed as attributes: