Prepare changelog for 1.7 release

[awaelchli]

What does this PR do?

Removes empty spaces and sets the date for today's release.

Before submitting

• Was this discussed/approved via a GitHub issue? (not for typos and docs)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests? (not for typos and docs)
• Did you verify new and existing tests pass locally with your changes?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or internal minor changes/refactorings)

PR review

Anyone in the community is free to review the PR once the tests have passed.
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Did you have fun?

I made sure I had fun coding 🙃

cc @tchaton @rohitgr7 @Borda @akihironitta

[codecov]

Codecov Report

Merging #13979 (3057804) into master (af07e75) will decrease coverage by 9%.
The diff coverage is n/a.

❗ Current head 3057804 differs from pull request most recent head 6f8a8e8. Consider uploading reports for the commit 6f8a8e8 to get more accurate results

@@            Coverage Diff            @@
##           master   #13979     +/-   ##
=========================================
- Coverage      86%      76%     -9%     
=========================================
  Files         341      341             
  Lines       26563    26563             
=========================================
- Hits        22732    20218   -2514     
- Misses       3831     6345   +2514