Fix requirements on values in `NSSet` and keys in `NSDictionary` #2209

Job	Run time
Check formatting	13s
Check MSRV	2m 9s
Lint macOS 64bit	3m 58s
Lint iOS 32bit	1m 31s
Lint GNUStep + exceptions	2m 35s
Lint header-translator	42s
Lint test-assembly	31s
Test macOS 12	4m 43s
Assembly tests	0s
Verify header translator output	0s
Check icrate features	0s
Compiler UI	0s
${{ matrix.name }}	0s
Test Compiler-RT	0s
${{ matrix.name }}	0s
Test on iOS simulator w. dinghy	0s
	16m 22s

Provide feedback