Strengthen mutable_set_v5 expect test against timing differences

[jmid]

The internal STM test mutable_set_v5.ml is currently run with --verbose which includes timing (0.0s) and subsequently diffed as an expect test. This creates the possibility of test failures due to a timing difference if it is run on a particular slow (CI) machine.

I just had this happen to me on the CI of an unrelated branch which happened to take 0.1s instead:
https://github.com/ocaml-multicore/multicoretests/actions/runs/6946194440/job/18897107446

STM test exception during next_state sequential failed with Random_next_state_failure as expected
STM test exception during next_state parallel failed with Random_next_state_failure as expected
diff --git a/_build/default/test/mutable_set_v5.expected b/_build/default/test/mutable_set_v5.output
old mode 100755
new mode 100644
index 84ab110..ef19a64
--- a/_build/default/test/mutable_set_v5.expected
File "test/mutable_set_v5.expected", line 1, characters 0-0:
/usr/bin/git --no-pager diff --no-index --color=always -u _build/default/test/mutable_set_v5.expected _build/default/test/mutable_set_v5.output
Command exited with code 1.
File "test/mutable_set_v5.expected", line 1, characters 0-0:
/usr/bin/git --no-pager diff --no-index --color=always -u _build/default/test/mutable_set_v5.expected _build/default/test/mutable_set_v5.output
Command exited with code 1.
+++ b/_build/default/test/mutable_set_v5.output
@@ -1,6 +1,6 @@
 
random seed: 229109553
 generated error fail pass / total     time test name
-
[ ]    0    0    0    0 /  100     0.0s STM sequential tests
[ ]    0    0    0    0 /  100     0.0s STM sequential tests (generating)
[✗]    2    0    1    1 /  100     0.0s STM sequential tests
+
[ ]    0    0    0    0 /  100     0.0s STM sequential tests
[ ]    0    0    0    0 /  100     0.0s STM sequential tests (generating)
[✗]    2    0    1    1 /  100     0.1s STM sequential tests
 
 --- Failure --------------------------------------------------------------------
 
Error: Process completed with exit code 1.

This little PR therefore removes the --verbose option for this expect test.

[jmid]

CI summary for 790cc71:

• FP 5.1 triggered a segfault in negative Lin CList int64 test with Effect [ocaml5-issue] Segfault with frame pointers in Effect test #394 [ocaml5-issue] Segfault in Lin Effect test in framepointer mode #416 (bug fixed on trunk)

Out of 63 workflows, 28 succeeded, 34 were canceled, 1 failed with a genuine failure

[jmid]

CI summary for 73d172c:

• MinGW bytecode trunk timeout during threadomain [ocaml5-issue] Windows failures on threadomain #203
• MinGW trunk failed - but is missing the relevant CI log!
• Cygwin 5.1 / part1 was cancelled
• Cygwin trunk / part1 was cancelled
• macos-arm64-5.0 found an unexpected counterexample in STM Sys test parallel STM parallel Sys tests on macOS #359

Out of 63 workflows, 58 succeeded, 2 were cancelled, 3 failed with 1 genuine error, 1 false alarm, 1 unknown (CI flaky)

[jmid]

CI summary for merge to main:

• Cygwin trunk / part1 failed with what looks like a network issue: InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-WebRequest], WebExc
• freebsd-amd64-5.1 timed out during 12444.9s Lin Out_channel test with Domain Long Out_channel shrinking runs cause timeout #378

Out of 38 workflows, 2 failed with 1 borderline testsuite/ocaml5 issue, and 1 CI network issue