Formatting and wording

JIRA is dead.

Actually I think we should put the 'other platforms' first & the more specific options at the end though

Moved Jira to "out of use" as it's now been archived.

See: https://github.com/civicrm/civicrm-core/pull/14184

Fix typo

Add CaseContact to hook_civicrm_post() and hook_civicrm_pre() documentation - see https://github.com/civicrm/civicrm-core/pull/14030

Reposition 'Campaign' in list to be alphabetical

show new way for accessing pr test site credentials

Much more could be done but this is probably worth doing as a light edit

Changing flush to clear as the preferred method. I think when it was added there was an assumption devs would be developing against < 5.4 so it made sense to give primacy to flush but times have changed

@totten