Discount code error message strips single quotes

[MaximilianoRicoTabo]

• Remove unwanted strip quotes function, esc_html should strip all unwanted chars.

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Changes proposed in this Pull Request:

Resolves #2882.

How to test the changes in this Pull Request:

1. Reproduce bug with steps from linked issue.
2. Apply this patch
3. Check issue does not happen anymore

Other information:

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• Have you successfully run tests with your changes locally?

Changelog entry

Enter a summary of all changes on this Pull Request. This will appear in the changelog if accepted.

[dparker1005]

My gut reaction was that pmpro_no_quotes() may have been used to protect strings when echoing this content into JS code. But since this content is not being outputted into JS code, it should be safe when wrapped in esc_html().

[MaximilianoRicoTabo]

I thought the same @dparker1005 , even more, went through history and saw how code evolved, pmpro_no_quotes was added like 10 years ago, and just several years later the esc_html function. Likely the intention was to strip odd chars and escape string and then several years ago esc_html function arrive to the WP ecosystem ? Not sure, perhaps we can ask Jason if he recall why was that function there.

[dparker1005]

I think you're probably right, but either way, this PR seems good to go