Convert all language returns to single quote

[MGatner]

Description
lang() requires single quotes in order to parse bracketed indexes. Mostly this is all correct but there are a few files still using double quotes. This PR converts these.

Checklist:

• Securely signed commits
• Component(s) with PHPdocs
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[jim-parry]

Oh crap - this is going to affect the codeigniter4/translations repo too.

[MGatner]

You're right. It looks like the same files in each locale are using double quotes.

What are your students up to this week? :)

[jim-parry]

They are working on localizations for the website. There, it doesn't matter about single vs double quotes, since all text gets passed through the template parser, sometimes after going through a markdown processor.

I'll raise an issue in the translations repo. At least there aren't as many translations there as for CI3!

[MGatner]

I feel confident a little awk-foo could take care of 90% of this - it just takes me an hour to figure out the actual command to use. Posting an issue is a good idea, maybe some awkmaster will stumble along and hav pity.