Use nightly scikit-image in upstream CI build

[jrbourbeau]

This fixes the

ERROR dask/array/tests/test_image.py - ValueError: numpy.dtype size changed, may indicate binary incompatibility. Expected 96 from C header, got 88 from PyObject

errors we're currently seeing in the upstream build due to scikit-image / NumPy 2.0 compatibility

[hendrikmakait]

Thanks, @jrbourbeau! LGTM assuming CI ends up being happy.

[github-actions]

Unit Test Results

See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests.

     15 files  +     12       15 suites  +12   3h 21m 46s ⏱️ + 3h 15m 54s
 13 121 tests +  7 795   12 190 ✅ +  7 638     931 💤 +   157  0 ❌ ±0 
162 468 runs  +154 861  142 438 ✅ +136 044  20 030 💤 +18 817  0 ❌ ±0 

Results for commit 2eb8f57. ± Comparison against base commit c619f1d.

[phofl]

thx