Remove invisible pagebreak chars from the standard library

[JosephSBoyle]

Following a discussion on a PR to clean up some unused vars in the email module: #102482,
there seemed to be a general feeling that we should remove invisible pagebreak characters (U+000C) from the standard library.

A quick ctrf-f with vscode shows <50 occurences which I proposed be deleted and optionally replaced with newlines. Each change should be checked for pep-8 compliance, in particular the 2-newlines rule.

I'm happy to submit a PR for this.

Linked PRs

• gh-102507 Remove invisible pagebreak characters #102531
• [3.11] gh-102507 Remove invisible pagebreak characters (GH-102531) #108266

[JosephSBoyle]

separate PR for removing pagebreaks following our conversation here: #102482

@AlexWaygood @warsaw