Remove `Greetings` Workflow

[purva-thakre]

Description

Fixes #2286

I chose Option 3 because the notifications are annoying when a person is working on a PR or is adding back-to-back issues.

The screenshot below is over a period of 5 minutes. The maintainers of this action are aware of the issue with the notifications spam but are not working on reducing these for those who are not new to the project.

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License

• [x] I license this contribution under the terms of the GNU GPL, version 3 and grant Unitary Fund the right to provide additional permissions as described in section 7 of the GNU GPL, version 3.

Before opening the PR, please ensure you have completed the following where appropriate.

• [x] I added unit tests for new code.
• [x] I used type hints in function signatures.
• [x] I used Google-style docstrings for functions.
• [x] I updated the documentation where relevant.
• [x] Added myself / the copyright holder to the AUTHORS file

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.22%. Comparing base (b58f029) to head (fbf3538). Report is 52 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2348 +/- ## ======================================= Coverage 98.22% 98.22% ======================================= Files 87 87 Lines 4056 4056 ======================================= Hits 3984 3984 Misses 72 72 ```

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