test: Remove unused sanitizer suppressions

* The GCC suppression was fixed in gcc-11, which is available on all LTS
  releases of Linux distros.
* The feerate suppression was likely fixed and does not trigger anymore.
  If it was to trigger again, the underlying bug should be fixed instead
  of suppressing it.
* The bench suppression does not trigger anymore.

Also, add comments to tsan suppressions on how to reproduce.

test/sanitizer_suppressions/tsan

@@ -13,6 +13,8 @@ race:zmq::*
 race:bitcoin-qt
 
 # deadlock (TODO fix)
+# To reproduce, see:
+# https://github.com/bitcoin/bitcoin/issues/19303#issuecomment-1514926359
 deadlock:Chainstate::ConnectTip
 
 # Intentional deadlock in tests
@@ -35,7 +37,7 @@ race:libzmq
 # https://github.com/bitcoin/bitcoin/issues/20618
 race:CZMQAbstractPublishNotifier::SendZmqMessage
 
-# https://github.com/bitcoin/bitcoin/pull/20218, https://github.com/bitcoin/bitcoin/pull/20745
+# https://github.com/bitcoin/bitcoin/pull/27498#issuecomment-1517410478
 race:epoll_ctl
 
 # https://github.com/bitcoin/bitcoin/issues/23366