Fix vale errors and warnings in the OpenID Connect (OIDC) and OAuth2 Client and Filters Reference Guide

[rolfedh]

@sberyozkin This is a quality update for main.
Do you approve backporting it to 3.2 as well?

Note: Here, I've made minimal changes to fix Vale errors and some warnings.
Related to QDOCS-536.

[quarkus-bot]

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The title of your pull request does not follow our editorial rules. Could you have a look?

• title should not end up with ellipsis (make sure the title is complete)

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[github-actions]

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[sberyozkin]

Thanks @rolfedh.

FYI, to avoid PR titles be stripped of some trailing words and the bot be unhappy the titles should be quite short, and indeed, the description can expand it, so I tried to shorten the title a bit, thanks 👍

[rolfedh]

the titles should be quite short

Thanks. I didn't realize this was an issue for our tooling. In the future, I'll use short titles and rely on the description to provide fuller information.

[gsmet]

Not backporting to 3.5 as doesn't apply cleanly. I will let @aloubyansky judge if he wants to backport that to 3.2 (I removed the label and then readded as it's not my call).

[michelle-purcell]

@rolfedh - Removing backport label as this guide is not being published for the 3.2 product doc release. Thanks.