Set `weights_only` in tests to avoid warnings in PyTorch 2.4 #13554

Job	Run time
pl-cpu (macOS-14, lightning, 3.10, 2.1)	14m 2s
pl-cpu (ubuntu-20.04, lightning, 3.10, 2.1)	13m 33s
pl-cpu (windows-2022, lightning, 3.10, 2.1)	15m 50s
pl-cpu (macOS-14, lightning, 3.10, 2.2)	13m 28s
pl-cpu (ubuntu-20.04, lightning, 3.10, 2.2)	13m 42s
pl-cpu (windows-2022, lightning, 3.10, 2.2)	15m 31s
pl-cpu (macOS-14, lightning, 3.10, 2.3)	13m 37s
pl-cpu (ubuntu-20.04, lightning, 3.10, 2.3)	14m 22s
pl-cpu (windows-2022, lightning, 3.10, 2.3)	15m 59s
pl-cpu (macOS-12, pytorch, 3.11, 2.1)	23m 44s
pl-cpu (ubuntu-22.04, pytorch, 3.11, 2.1)	14m 10s
pl-cpu (windows-2022, pytorch, 3.11, 2.1)	14m 37s
pl-cpu (macOS-13, lightning, 3.8, 2.1, oldest)	19m 52s
pl-cpu (ubuntu-20.04, lightning, 3.8, 2.1, oldest)	11m 5s
pl-cpu (windows-2022, lightning, 3.8, 2.1, oldest)	15m 3s
pl-cpu (macOS-14, pytorch, 3.8, 2.1)	14m 39s
pl-cpu (ubuntu-20.04, pytorch, 3.8, 2.1)	13m 43s
pl-cpu (windows-2022, pytorch, 3.8, 2.1)	14m 32s
	4h 31m 29s

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