Remove now-unused WITNESS_STRIPPED variant of TxValidationResult #156

Job	Run time
macOS 14 native, arm64, fuzz	12m 41s
macOS 14 native, arm64, no depends, sqlite only, gui	22m 42s
Linux->Windows cross, no tests	57m 53s
Windows native, VS 2022	1h 39m 11s
Windows native, fuzz, VS 2022	34m 33s
ASan + LSan + UBSan + integer, no depends, USDT	1h 7m 5s
test each commit	0s
Windows, test cross-built	41m 38s
	5h 35m 43s

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