[client] Prepare client python migration and read only (#1031)

[aHenryJard]

Proposed changes

• Update README.md
• Remove renovate configuration

Related issues

• relates to Move client-python into opencti repository and change the client-python to read-only #1031

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...