gh-130154: Pygettext: allow extracting constant f-strings

[tomasr8]

For more details, see the linked issue, but the gist is:

with this PR, this is now extracted:

_(f'foo')

while this remains disallowed:

_(f'foo {x}')

Feedback welcome!

cc @StanFromIreland in case you're interested ;)

• Issue: Pygettext: allow extracting constant f-strings #130154

[StanFromIreland]

Suggested change

	if value is not None:
	return value
	return self._parse_literal_fstring(node)
	return self._parse_literal_string(node) or self._parse_literal_fstring(node)

[tomasr8]

self._parse_literal_string(node) could return '' which is falsey so we'd try to parse an f-string there which is not what we want