Fix requirements on values in `NSSet` and keys in `NSDictionary` #2206

Job	Run time
Lint macOS 64bit	3m 40s
Lint iOS 32bit	1m 22s
Lint GNUStep + exceptions	3m 28s
Lint header-translator	40s
Lint test-assembly	37s
Check formatting	13s
Check MSRV	1m 29s
Test macOS 12	5m 10s
Compiler UI	2m 6s
Assembly tests	1m 3s
Verify header translator output	1m 0s
Check icrate features	0s
Test Compiler-RT	46s
${{ matrix.name }}	0s
Test GNUStep with libobjc2 v1.9	1m 46s
Test GNUStep with libobjc2 v2.0	1m 54s
Test GNUStep with libobjc2 v2.1 on nightly	1m 34s
Test GNUStep 32bit	1m 54s
Test on iOS simulator w. dinghy	0s
	28m 42s

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