docs[installation]: Add CCD sync to test setup instructions

[Emrys-Merlin]

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ℹ️ PR Description

Hi :)

I could not follow the dev setup instructions exactly, because I ran into two issues:

1. aw setup tests failed if I did not setup the PDB_MIRROR_PATH variable beforehand.
2. After running aw setup tests successfully, ca. half the tests still failed due to missing CCD codes. In fact, no tests/data/ccd directory was created contrary to my expectation. The artifact test_pack_latest.tar.gz did not contain any CCD data and the setup code does not seem to try to download the CCDs (in contrast to the missing PDBs).

I am not sure if the issue should be addressed on the documentation level or if aw setup tests should be adapted (or something else entirely). I thought updating the docs is very low effort. So, I just went ahead. If you prefer to address the issue another way or if I simply made a mistake during setup, I'm happy to close the PR.

What changes were made and why?

1. I switched point 1 and 2 in the instructions, which instructs users to set up the ENV variables before running aw setup tests.
2. I added aw ccd sync tests/data/ccd to the (new) second point to make sure that CCD data is available.

How were the changes tested?

I ran the test suite. Without the changes ca. half the tests failed. After these fixes, all but one¹ test passed and the failing test seems unrelated to the downloaded data.

Additional Notes

Footnotes

1. The failing test is a regression test, namely: tests/io/components/test_regression.py::test_regression_against_stored_result[1twr]. There was a mismatch in charges for 4 atoms. ↩