Remove leftover unnecessary R| formatting

[joshuacwnewton]

Checklist

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Description

This is a tiny PR with just cosmetic changes: With #3361, raw-text formatting is now applied by default to all descriptions (without the need for R|), so I removed those bits of text.

Also, while I was here, I cleaned up the docstrings for SmartFormatter in f3da9b9, since one of them referenced R|.

Linked issues

Fixes #3546.

[jcohenadad]

I come late to the party so i'm not sure exactly when (and why) the _textwrap feature from the parser was removed, but is there a plan to make it look the way it was before?

the way it looks now:

the way it looked on 5.1.0:

[joshuacwnewton]

I come late to the party so i'm not sure exactly when (and why) the _textwrap feature from the parser was removed

_textwrap isn't available in Python 3.7 (context: #2782), so the old snippets of code we copy-pasted from argparse had broken once we upgraded.

I was assuming that argparse had replaced _textwrap internally with a 3.7-compatible code. But I now see that (as you've pointed out), the changes I made were not identical to the previous copy-pasted code.

Thank you for noticing! I'll dig a little deeper to find out what argparse did once _textwrap broke.

[joshuacwnewton]

Merging this now, but I'll follow up on the formatting in #3562.