Improve clarity and correctness in RRF documentation

[elharo]

Refined language and clarified concepts regarding Remote Repository Filtering in Maven documentation.

[cstamas]

Can you pls take a peek at #1794 as well?

[cstamas]

@elharo I plan release today/tomorrow (soon), can you finish this in this timeframe or should I go along with release (we planned last week the release, but we got bugreports that had to be fixed, goal is doing maven 3.9.13/4-rc-6 that both depends on resolver release).

[cstamas]

I scheduled this and #1794 for release 2.0.15. Please ping back during this workday (EU timezone), as I would like to release 2.0.15 very soon, and I don't consider these pages essential for that (bugfix) release. Worst can happen is that we have these two PRs in 2.0.16 (next) release.

[elharo]

I haven't finished going through the entire doc yet, and I might not finish that today, but if you want to take this much as is, it's still an improvement.

[cstamas]

Iterating over is just fine, we can always improve step by step.

[github-actions]

@cstamas Please assign appropriate label to PR according to the type of change.