Drop liburcu-related TSAN suppressions

They are not needed with TSAN-aware custom liburcu.

Images with custom liburcu were pulled out as the gcc:asan job was crashing. A new approach is needed.

Validation pipelines with special images for TSAN jobs:

• main - https://gitlab.isc.org/isc-projects/bind9/-/pipelines/138422 & https://gitlab.isc.org/isc-projects/bind9/-/pipelines/138423
• bind-9.18 - https://gitlab.isc.org/isc-projects/bind9/-/pipelines/138425
• bind-9.16 - https://gitlab.isc.org/isc-projects/bind9/-/pipelines/138426 (respdiff-*:tsan failure is #4034 (closed))

isc-projects/images!243 needs to be merged first.