doc: address various uses of "obvious" and "obviously"

In one instance, the sentences are unnecessarily long. Simplify the text.

In another instance, the sentence is unnecessary. Remove it.

In two other instances, deleting "obvious(ly)" seems to improve the documentation.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• documentation is changed or added
• commit message follows commit guidelines