Fix LGTM code analysis warnings

[pierlon]

Summary

Fixes #6587.

Checklist

• My code is tested and passes existing tests.
• My code follows the Engineering Guidelines (updates are often made to the guidelines, check it out periodically).

[lgtm-com]

This pull request fixes 13 alerts when merging 776ceca into c8f6f6f - view on LGTM.com

fixed alerts:

• 4 for Unused variable, import, function or class
• 3 for Unused import
• 2 for Useless conditional
• 1 for Module is imported more than once
• 1 for Unused local variable
• 1 for Superfluous trailing arguments
• 1 for Module is imported with 'import' and 'import from'

[github-actions]

Plugin builds for 3a7f9cc are ready 🛎️!

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[lgtm-com]

This pull request fixes 13 alerts when merging dc849e8 into ed78087 - view on LGTM.com

fixed alerts:

• 4 for Unused variable, import, function or class
• 3 for Unused import
• 2 for Useless conditional
• 1 for Module is imported more than once
• 1 for Unused local variable
• 1 for Superfluous trailing arguments
• 1 for Module is imported with 'import' and 'import from'

[lgtm-com]

This pull request fixes 13 alerts when merging 3a7f9cc into a8706f7 - view on LGTM.com

fixed alerts:

• 4 for Unused variable, import, function or class
• 3 for Unused import
• 2 for Useless conditional
• 1 for Module is imported more than once
• 1 for Unused local variable
• 1 for Superfluous trailing arguments
• 1 for Module is imported with 'import' and 'import from'

[swissspidy]

Theoretically you could have also done @return {import('react').ReactElement} Element.

[pierlon]

Hmm yea, I think that would require us disabling the jsdoc/valid-types ESLint rule though. We're currently using the @wordpress/eslint-plugin/recommended-with-formatting plugin which in turn adds JSX as a valid type.