remove redundant sections about keyword independence

[gregsdennis]

What kind of change does this PR introduce?

Clarification

Issue & Discussion References

• Closes Section "Keyword independence" is written twice #1218

Summary

Removes 2 redundant sections about keywords being independent. We now have a "Keyword Independence" section, and each keyword section explicitly states their relations to other keywords.

Does this PR introduce a breaking change?

No

[jdesrosiers]

In case anyone else is trying to find where this was stated elsewhere, it's in the "Keyword Interactions" section line 487.

### Keyword Interactions

Unless otherwise specified, keywords act independently.

Keywords MAY modify their behavior based on the presence, absence, or value of
another keyword in the same schema object. Such keywords MUST NOT result in a
circular dependency.

Supplementary specifications are encouraged to specify any dependencies as part
of the dependent keyword (i.e. the keyword whose behavior is modified).

Within this document, keyword dependencies are expressed using one of the
following mechanisms:

- Static dependencies, in which the dependency relies on the presence or
  contents of another keyword.
- Dynamic dependencies, in which the dependency relies on the evaluation of
  another keyword against an instance. This dependency may be on either the
  annotations produced by the keyword or the validation result of its
  subschema(s).

These mechanisms are used merely to describe dependencies; they are for
illustrative purposes and not prescriptive. Implementations MAY use whatever
mechanisms make sense given the needs of their architecture and language in
order to achieve the specified behaviors.

So with this change, we are no longer being explicit about which keywords violation the keyword independence principle. I think that's fine.