Fix wrong information in Documentation

[MarleneKress79789]

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1. in dev docu: build and then download build archive is very strange. remove mention of download
2. need to updated dev docu: run tests should now be done using nox, also needs to mention starting db
3. user guide: "python -m exasol_transformers_extension.deploy language-container --version 0.5.0 ..." tries to download slc from github but does not seem to exist (might be a wrong name issue)
4. deployment.deployment_utils.py : should be: GH_RELEASE_URL = "https://github.com/exasol/transformers-extension/releases/tag" (No this is correct as is)

[MarleneKress79789]

Number 3 and 4 where fixed in #134