Update composer update documentation

[nick-vanpraet]

Also updated vale documentation link.

I believe I did not tell a lie, but best to have a few eyes on it. I left in all the git stuff, even though nothing mentions you should use git or what it even is but I felt that was out of scope for now.

[RCheesley]

Some vale fixes based on the test failures.

Does this also hold true for people using Composer with Recommended Project? Do we also need to warn about for example htaccess which might have custom modifications?

[nick-vanpraet]

Does this also hold true for people using Composer with Recommended Project? Do we also need to warn about for example htaccess which might have custom modifications?

This is specifically for people using Recommended Project. Which is the only mention I see in the setup doc pages, so I figure that is the only one we officially support. Anyone who adds packages themselves to their own composer they setup on their own should know enough to manage regardless.

The warnings about git diff and .htaccess are all still present, I just added 2 extra bullet points before the existing ones and rewrote the one that said to run composer update mautic/core-lib.

[RCheesley]

I do think we should clarify the bit about using git diff and when it would be used, but that can be done in another PR.