[Messenger] Add reference to PHP docs for SSL context options

[phansys]

Follows #20094 (comment).

[MrYamous]

Suggested change

	The ``ssl`` option can be used to provide SSL context options (`php.net/context.ssl`_) for the TLS channel, e.g. in tests:
	The ``ssl`` option can be used to provide `SSL context options`_ for the TLS channel, e.g. in tests:

WDYT about this for better link integration in text ?

[phansys]

I think we could use the proposed variant if this keeps the reference intact to the PHP docs.

See:

symfony-docs/components/cache/adapters/redis_adapter.rst

Line 220 in f39f657

SSL context options. See `php.net/context.ssl`_ for more information.

[javiereguiluz]

Yes, @MrYamous proposal is what we usually do in the docs. So, I changed this while merging. See 714113c

[javiereguiluz]

Thanks Javier!