* Meta: Document expectations for changing existing PEPs in contrib guide
* Meta: Clarify commit message/PR title prefixes in contrib guide
* Meta: Further improve change policy in CG per Jelle's feedback
* Meta: Reduce verbosity and perscriptiveness of changes section in CG
* Meta: Move more general/normative PEP modification guidance to PEP 1
* Meta: Further revise PEP change guidance to reflect current reality
* Meta: Update, simplify and consolidate guidance on changing PEPs
* PEP 1: Remove sentence explicitly discussing changing governance PEPs