Add another UBSAN vptr suppression

Summary:
The recent UBSAN failures ( example: https://build.bitcoinabc.org/viewLog.html?buildId=32136&buildTypeId=BitcoinABC_Master_BitcoinAbcMasterUbsan&tab=buildLog&_focus=2561 ) appear to be triggered by a recent patch ( D5527 ) but I can find no definite root cause within that patch itself. I am able to reproduce this error with clang-8, but tests pass building with clang-9.

Similar to D4848, the exact root cause of this vptr issue is unknown. This patch adds a similar suppression.

Test Plan:

ABC_BUILD_NAME=build-ubsan ./contrib/teamcity/build-configurations.sh

export UBSAN_OPTIONS="suppressions=/home/jasonbcox/projects/bitcoin-abc/test/sanitizer_suppressions/ubsan:print_stacktrace=1:halt_on_error=1"
./test/functional/test_runner.py wallet_multiwallet

+ UBSAN on CI

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5535