increase the timeout for 'tasyncclosestall' (#12744)
increase the timeout for 'tasyncclosestall' (#12744)

This test is very flaky, this change might help reducing the
number of failings (usually solved by restarting the test suite).

Refs https://github.com/nim-lang/Nim/pull/12694#issuecomment-557583790
dom96/Nim,dom96/Nim,dom96/Nim,dom96/Nim,dom96/Nim,dom96/Nim,dom96/Nim