[Submission listings] Remove enable_new_submission_listing config option and code hidden behind it

[asmecher]

Valid Title

• I have updated the title to accurately reflect the bug description

Description

Before RC2 goes out, we need to remove the enable_new_submission_listing option in config.inc.php, and remove the old submission list code that's currently hidden behind it when disabled.

Steps to Reproduce

(n/a)

Expected Result

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Actual Result

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Environment Details

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Application Version

OJS, OMP, OPS 3.5.0

Logs

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Additional Information

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[asmecher]

@jardakotesovec and @Vitaliy-1, assigning this to the two of you; this code removal should definitely happen before RC2 goes out, so RC2 testing can help ensure we don't accidentally remove something critical. If either of you have this filed elsewhere, please mark it as a dupe! I couldn't find anything.