Pin `keras` version to 3.5.0 #686

Job	Run time
Check Linting	15s
Check Manifest	19s
Run brainmapper tests to check for breakages	12m 37s
Run tests with numba disabled	14m 36s
Run package tests (ubuntu-latest, 3.10)	6m 45s
Run package tests (ubuntu-latest, 3.11)	6m 44s
Run package tests (ubuntu-latest, 3.12)	7m 29s
Run package tests (macos-latest, 3.12)	3m 55s
Run package tests (windows-latest, 3.12)	8m 3s
Build source distribution and wheel	0s
Publish build distributions	0s
	1h 0m 43s

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