Clean up changelog.txt from duplicate entries

[afercia]

Description

Splitting this out from a conversation on Slack.

It appears in the changelog.txt file the entries for the = 19.7.0 = release are duplicated. Not sure about other dupplicates.

GitHub can't show such a long file but here's the referenced section, starting at line 1298 and line 1837:

• https://github.com/WordPress/gutenberg/blob/35e99d41b6182c44f2e074bf29ad8e5b80d25ac5/changelog.txt#L1298
• https://github.com/WordPress/gutenberg/blob/35e99d41b6182c44f2e074bf29ad8e5b80d25ac5/changelog.txt#L1837

The entries have been added in two separate autogenerated commits:

• 603e5c0
• fe70c12

Step-by-step reproduction instructions

N/A

Screenshots, screen recording, code snippet

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Environment info

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Please confirm that you have searched existing issues in the repo.

• Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

• Yes

Please confirm which theme type you used for testing.

• Block
• Classic
• Hybrid (e.g. classic with theme.json)
• Not sure