doc: tweak install & setup guide

added feedback from @benediktwoelk

task: https://gitlab.opencode.de/opencode-analyzer/management/-/work_items/73

link to main readme: https://gitlab.opencode.de/opencode-analyzer/data-provider/-/blob/doc/install_and_setup_review/README.md?ref_type=heads

direct link to install & setup guide: https://gitlab.opencode.de/opencode-analyzer/data-provider/-/blob/doc/install_and_setup_review/doc/install_and_setup.md

Acceptance Criteria

The following acceptance criteria are defined regarding the result of this story:

• A new developer is able to ...
  1. ... set up a local dev-environment
  2. ... run the projects default tests
  3. ... follow all other project related guides e.g. development guide, administration tasks.