Ensure static-learning adds rewritten assertions. (#5982)

Ensure static-learning adds rewritten assertions. (#5982)

The static-learning preprocessing sometimes added non-rewritten assertions, despite being used in a part of the preprocessor that assumes all assertions to be rewritten. This may then break other passes further down, in the case of #5729 the non-clausal simplification which explicitly asserts that assertions are rewritten. This PR rewrites the respective assertion properly in the static-learning pass.
Fixes #5729.