Remove duplicated changelog entry for 5521

[dbeatty10]

The changelog for 1.3 already has the following entry, so removing it for the changelog for 1.4:

Migrate dbt-utils current_timestamp macros into core + adapters (#5521, #5838)

[dbeatty10]

I tried adding [skip ci] to my commit to bypass running all the CI checks. With my level of permissions, that left the PR in an unmergable state since "required statuses must pass before merging". So I used an empty commit to get things going again:

git commit --allow-empty -m "Empty commit to bump CI"