The test_moderately_small_alpha dirichlet test fails for 32-bit Windows Python3.13t
wheel builds due to a memory error. Decrease the size of the test array by a bit.

Note that this test is only run for the mt19937 generator.

I don't know if this is a problem due to the free threading update, or a change
in the build infrastructure. Another solution would be to use try-except or a loop, but I
think decreasing the number of testedalpha is preferable -- if it works.