swift234

Decrease the probability that stdlib/Hashing.swift will fail

Bump the number of trials from 10 to 14, which makes the test orders of
magnitude less likely to fail.  For a range of size 10, doing 10 trials
meant that a single call to checkRange would fail ~0.03% of the time;
with 14 trials the spurious failure rate is ~0.0003%. We have 10 calls
to checkRange in this test with ranges of size <= 10.

While this test didn't fail that often before, we have a very large
number of automated builds and it has been a constant low-level source
of friction that this test fails and we have to look at and then ignore
the results.