text: Title: Remove LGTM badges from README, and remove LGTM comments from code
  Body: <img width="863" alt="Screenshot 2022-12-17 at 00 14 31" src="https://user-images.githubusercontent.com/350976/208211980-bb8add5f-5c49-4b47-ac1b-8f58e8e67dcb.png">
  
  LGTM was a security checker we used for Piccolo. It has now been shut down, and replaced with Github code scanning.
  
   * Remove the badges from README.md (see attached image)
   * Search the codebase for any LGTM comments, and remove them (they start with `# lgtm`), for example `# lgtm [py/missing-equals]`.