fix sentence in message_after_copy

[sjvrijn]

Checklist before requesting a review

• I have read the contribution guidelines
• I have performed a self-review of my code
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

List of related issues or pull requests

Refs:

• Improve message.yml #641

Describe the changes made in this pull request

Replaced the sentence as suggested in the issue.

Instructions to review the pull request

Install the requirements

cd $(mktemp -d --tmpdir py-tmpl-XXXXXX)
pip install pipx
pipx install copier

Create a new package using the template

copier copy --vcs-ref <YOUR_BRANCH> https://github.com/nlesc/python-template test_package

[egpbos]

This is amazing work, thank you so much for this effort @sjvrijn! Apologies that my review took so long, but I wanted to take the time to properly study the repercussions of this on adjacent concerns 😜