Docs: spelling and grammar fixes

Why is this change being made?

Spelling and grammar fixes as part of my read-through of the Configure documentation as I train to become the technical writer for that stage: gitlab-org/technical-writing#137 (closed)

Does this MR meet the acceptance criteria?

Assign to DRI

• Did you assign this change to the correct DRI of the page or information you are changing?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what