test: remove timers-blocking-callback

If the bug this test is intented to catch is reintroduced, or if 5aac4c4 is effectively reverted, many (50+) tests time out, rendering this test redundant and unnecessary.

in particular, the following timer tests catch an effective revert of 5aac4c4:

not ok 21 parallel/test-timers-api-refs
not ok 22 parallel/test-timers-args
not ok 23 parallel/test-timers-destroyed
not ok 25 parallel/test-timers-nested
not ok 26 parallel/test-timers-interval-throw
not ok 28 parallel/test-timers-non-integer-delay
not ok 32 parallel/test-timers-ordering
not ok 33 parallel/test-timers-refresh
not ok 34 parallel/test-timers-refresh-in-callback
not ok 35 parallel/test-timers-reset-process-domain-on-throw
not ok 40 parallel/test-timers-timeout-to-interval
not ok 41 parallel/test-timers-uncaught-exception
not ok 42 parallel/test-timers-timeout-with-non-integer
not ok 43 parallel/test-timers-unenroll-unref-interval
not ok 44 parallel/test-timers-unref
not ok 45 parallel/test-timers-unref-active
not ok 46 parallel/test-timers-unrefd-interval-still-fires
not ok 47 parallel/test-timers-unrefed-in-callback
not ok 48 parallel/test-timers-user-call
not ok 49 parallel/test-timers-zero-timeout

Refs: #21781

test/sequential/sequential.status

@@ -17,8 +17,6 @@ test-worker-prof: PASS, FLAKY
 [$system==linux]
 
 [$system==macos]
-# https://github.com/nodejs/node/issues/21781
-test-timers-blocking-callback: PASS, FLAKY
 
 [$system==solaris] # Also applies to SmartOS