tuple slice should not propagate fallback #11234

Job	Run time
Test mypyc suite with 32-bit Python	10m 25s
Test suite with py38-ubuntu, mypyc-compiled	23m 1s
Test suite with py38-windows-64	31m 37s
Test suite with py39-ubuntu	24m 32s
Test suite with py310-ubuntu	28m 51s
Test suite with py311-ubuntu, mypyc-compiled	21m 23s
Test suite with py312-ubuntu, mypyc-compiled	24m 14s
mypyc runtime tests with py38-macos	9m 31s
mypyc runtime tests with py38-debug-build-ubuntu	8m 22s
Type check our own code (py38-ubuntu)	2m 53s
Type check our own code (py38-windows-64)	3m 3s
Formatting and code style with Black + ruff	42s
	3h 8m 34s

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