Update Saltstack instructions

[JonathanTreffler]

I tried following the existing instructions, but they are outdated and failed with "failed building wheels" errors, so I updated them and improved the way the necessary dependencies are installed.

(Note: I could not get pygit2 to work, even trying to compile it from source did not work, so I left this instruction as is, maybe it works for someone. I don't need pygit so I don't want to invest more time in trying to fix it)

[nichtmax]

Works for me with python 3.12 without any version pinning:

[moritz@stardust ~]$ python3.13 -m venv ~/salt_venv
[moritz@stardust ~]$ source ~/salt_venv/bin/activate
(salt_venv) [moritz@stardust ~]$ pip install salt
Looking in indexes: https://pypi.org/simple/
Collecting salt
  Downloading salt-3007.11.tar.gz (16.2 MB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 16.2/16.2 MB 9.8 MB/s eta 0:00:00
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
  Preparing metadata (pyproject.toml) ... done
Building wheels for collected packages: salt
  Building wheel for salt (pyproject.toml) ... done
  Created wheel for salt: filename=salt-3007.11-py3-none-any.whl size=6189639 sha256=bcbb9da77b8b59f6177e2feeacf47c9c98ee8dd1185c1a7ee26780eb8900351c
  Stored in directory: /home/moritz/.cache/pip/wheels/df/f2/56/42b34c73fae532284de6365566d8b2871256cfd78779f14373
Successfully built salt
Installing collected packages: salt
Successfully installed salt-3007.11

[notice] A new release of pip is available: 25.0.1 -> 25.3
[notice] To update, run: pip install --upgrade pip
(salt_venv) [moritz@stardust ~]$ 

pygit2 fails because of gcc, we can't update gcc with Uberspace 7 unfortunately