Ignore changelog when running textlint

[ferrarimarco]

Proposed changes

The changelog is automatically generated, so we ignore it when running textlint because some terms might have been lowercased.

Readiness checklist

In order to have this pull request merged, complete the following tasks.

Pull request author tasks

• I included all the needed documentation for this change.
• I provided the necessary tests.
• I squashed all the commits into a single commit.
• I followed the Conventional Commit v1.0.0 spec.
• I wrote the necessary upgrade instructions in the upgrade guide.
• If this pull request is about and existing issue,
  I added the Fix #ISSUE_NUMBER label to the description of the pull request.

Super-linter maintainer tasks

• Label as breaking if this change breaks compatibility with the previous released version.
• Label as either: automation, bug, documentation, enhancement, infrastructure.