Remove the lightning app code #13523

Job	Run time
pl-cpu (macOS-14, lightning, 3.10, 2.1)	14m 54s
pl-cpu (ubuntu-20.04, lightning, 3.10, 2.1)	14m 39s
pl-cpu (windows-2022, lightning, 3.10, 2.1)	16m 23s
pl-cpu (macOS-14, lightning, 3.10, 2.2)	14m 14s
pl-cpu (ubuntu-20.04, lightning, 3.10, 2.2)	14m 41s
pl-cpu (windows-2022, lightning, 3.10, 2.2)	15m 18s
pl-cpu (macOS-14, lightning, 3.10, 2.3)	14m 18s
pl-cpu (ubuntu-20.04, lightning, 3.10, 2.3)	15m 17s
pl-cpu (windows-2022, lightning, 3.10, 2.3)	16m 30s
pl-cpu (macOS-12, pytorch, 3.11, 2.1)	24m 36s
pl-cpu (ubuntu-22.04, pytorch, 3.11, 2.1)	14m 30s
pl-cpu (windows-2022, pytorch, 3.11, 2.1)	16m 38s
pl-cpu (macOS-13, lightning, 3.8, 2.1, oldest)	20m 25s
pl-cpu (ubuntu-20.04, lightning, 3.8, 2.1, oldest)	12m 27s
pl-cpu (windows-2022, lightning, 3.8, 2.1, oldest)	14m 21s
pl-cpu (macOS-14, pytorch, 3.8, 2.1)	15m 4s
pl-cpu (ubuntu-20.04, pytorch, 3.8, 2.1)	14m 44s
pl-cpu (windows-2022, pytorch, 3.8, 2.1)	15m 34s
	4h 44m 33s

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