TestConvolve2d.test_large_array failing on Windows ILP64 CI job

[rgommers]

I've seen this test fail multiple times now, for example on gh-12374. The test was recently introduced in gh-12238. That test job uses more memory than other tests I suspect, so maybe this is a matter of reducing the allocated array size a little. @peterbell10 any thoughts on this one?

_______________________ TestConvolve2d.test_large_array _______________________
[gw0] win32 -- Python 3.8.5 C:\hostedtoolcache\windows\Python\3.8.5\x64\python.exe
C:\hostedtoolcache\windows\Python\3.8.5\x64\lib\site-packages\scipy\signal\tests\test_signaltools.py:422: in test_large_array
    count = signal.convolve2d(a, [[1, 1]])
        a          = array([[1, 0, 1, ..., 0, 1, 0],
       [0, 1, 0, ..., 1, 0, 1],
       [1, 0, 1, ..., 0, 1, 0],
       ...,
       [1, 0, 1, ..., 0, 1, 0],
       [0, 1, 0, ..., 1, 0, 1],
       [1, 0, 1, ..., 0, 1, 0]], dtype=int64)
        n          = 268435
        self       = <scipy.signal.tests.test_signaltools.TestConvolve2d object at 0x0000020362515790>
C:\hostedtoolcache\windows\Python\3.8.5\x64\lib\site-packages\scipy\signal\signaltools.py:1689: in convolve2d
    out = sigtools._convolve2d(in1, in2, 1, val, bval, fillvalue)
E   MemoryError: Unable to allocate 2.00 GiB for an array with shape (268435, 1001) and data type int64