Fix `jest/no-conditional-expect` lints throughout the codebase

[weeman1337]

This is a follow-up to matrix-org/matrix-react-sdk#10261, sister issue tracking the same thing in the matrix-js-sdk repo,*

There are many jest/no-conditional-expect lints throughout the codebase that we should refactor away at some point.

The rule is currently disabled in .eslintrc.js