Fix test failure on fast machine (release builds)

[greg7mdp]

When I build in release mode, I have the following tests failing (both gcc-12 and clang-16, no problem in debug)

/home/greg/github/enf/leap/unittests/api_tests.cpp(1078): error: in "api_tests/checktime_pause_max_trx_cpu_extended_test": elapsed 26100us 
/home/greg/github/enf/leap/unittests/api_tests.cpp(1136): error: in "api_tests/checktime_pause_max_trx_extended_test": elapsed 26056us

This is the first failure in the code:

   // This assumes that loading the WASM takes at least 1.5 ms
   // If this check fails but duration is >= 24'999 (previous check did not fail), then the check here is likely
   // because WASM took less than 1.5 ms to load.
   BOOST_CHECK_MESSAGE( dur > 26'500, "elapsed " << dur << "us" );

I also have the following failure occasionally when building in release with gcc-12.

/home/greg/github/enf/leap_main/unittests/api_tests.cpp(1351): error: in "api_tests/checktime_hashing_fail": exception deadline_exception expected but not raised

So lowering deadline from 10ms to 8ms.