Remove APIs from web renderers that are banned in google internal repository

[jacobsimionato]

Some API used in the open source codebase are banned in google's repo e.g. unsafeHTML.

We need to remove these and ideally set up some CI to prevent them being readded.

See https://docs.google.com/document/d/18JP9Gctrtwkvxvx2hZ59zhdJNrLffRRyXvR9u-SC5JE/edit?tab=t.0 for context

[jacobsimionato]

This problem may be related to MarkdownIt code, so if we use g3 markdown, it is not a problem.

To be checked!