docs(accessibility-testing): Updates content as part of content audit. (

patternfly#3776)

* docs(accessibility-testing): Updates content as part of content audit.

* Apply suggestions from code review

Co-authored-by: Eric Olkowski <[email protected]>

* Apply suggestions from code review

* Content tweaks in progress.

* Works on checkboxes.

* Resolves merge conflict.

* Update packages/documentation-site/patternfly-docs/content/developer-resources/accessibility-testing.md

* Update packages/documentation-site/patternfly-docs/content/developer-resources/accessibility-testing.md

Co-authored-by: Eric Olkowski <[email protected]>

* Update packages/documentation-site/patternfly-docs/content/developer-resources/accessibility-testing.md

Co-authored-by: Eric Olkowski <[email protected]>

* Content alterations.

* Content changes from review feedback.

* Updates to buttons point.

* Grammar and typo updates.

* Update packages/documentation-site/patternfly-docs/content/developer-resources/accessibility-testing.md

Co-authored-by: Eric Olkowski <[email protected]>

* Merging.

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Co-authored-by: Eric Olkowski <[email protected]>