test: Add tsan supp for leveldb::DBImpl::DeleteObsoleteFiles

Summary:
Fixes issue core#19712: Data race detected when running rpc_blockchain.py

This is a backport of core#19830

Test Plan:
With TSAN:
ninja check-functional

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10137