tests: Remove no longer needed UBSan suppressions

Summary:
core#20379

Remove no longer needed UBSan suppression.
The float divide-by-zero in validation.cpp was fixed by instagibbs in D8857.

The other suppression was removed by core#19630 after fixing fee estimation code that does not exist in Bitcoin ABC. We can assume that we do not need this suppression, and add it back if needed.

This is a backport of core#20379

Test Plan:
With UBSAN:
ninja && ninja check check-functional

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10728