[dead-code] Skip substr casting removal on PHP 7.x, as can return false|string #31713

Job	Run time
End to end test - e2e/applied-auto-import	21s
End to end test - e2e/applied-polyfill-php80	27s
End to end test - e2e/applied-rule-removed-node	21s
End to end test - e2e/applied-rule-return-array-nodes	16s
End to end test - e2e/applied-rule-change-docblock	27s
End to end test - e2e/no-parallel-reflection-resolver	17s
End to end test - e2e/only-option	20s
End to end test - e2e/only-option-quote-double-equalnone	21s
End to end test - e2e/only-option-quote-single	24s
End to end test - e2e/invalid-paths	19s
End to end test - e2e/only-option-quote-single-bsdouble	20s
End to end test - e2e/parallel-reflection-resolver	19s
End to end test - e2e/parallel-custom-config	21s
End to end test - e2e/parallel with space	19s
End to end test - e2e/parallel-kaizen-applied-rules	21s
End to end test - e2e/only-option-quote-single-equalnone	20s
End to end test - e2e/different-path-over-skip-config	24s
End to end test - e2e/print-new-node	22s
	6m 19s

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