[TwigComponent] Remove floating text in documentation

[alexislefebvre]

Q	A
Bug fix?	no
New feature?	no
Deprecations?	no
Documentation?	yes
Issues	-
License	MIT

This looked weird:

[Kocal]

I think the current goal of this text is to behave like a <figcaption>, thus I suggest to keep it, but improve its current display.

cc @javiereguiluz, do you know if Symfony RST is able to handle <figure> and <figcaption>? Thanks

[javiereguiluz]

No. We just generate simple <img>. For example, this RST code:

.. image:: /_images/components/console/completion.gif
    :alt: The terminal completes the command name "secrets:remove" and the argument "SOME_OTHER_SECRET".

When rendering the HTML page (https://symfony.com/doc/current/console.html) it generates this HTML code:

<img src="/doc/7.3/_images/completion.gif" alt="The terminal completes the command name &quot;secrets:remove&quot; and the argument &quot;SOME_OTHER_SECRET&quot;.">

[Kocal]

Alright, thanks!

[Kocal]

Thank you @alexislefebvre.