Redundant checks in ResponseCachingKeyProvider

There are two places, where Null-Conditional Operator (`?.`) using seems redundant in `CreateStorageVaryByKey()` method of `internal class ResponseCachingKeyProvider`.

https://github.com/dotnet/aspnetcore/blob/6ae3ea387b20f6497b82897d613e9b8a6e31d69c/src/Middleware/ResponseCaching/src/ResponseCachingKeyProvider.cs#L99

and

https://github.com/dotnet/aspnetcore/blob/6ae3ea387b20f6497b82897d613e9b8a6e31d69c/src/Middleware/ResponseCaching/src/ResponseCachingKeyProvider.cs#L126

There is sufficient check of `varyByRules` value at the start of the method. Isn't it?

https://github.com/dotnet/aspnetcore/blob/6ae3ea387b20f6497b82897d613e9b8a6e31d69c/src/Middleware/ResponseCaching/src/ResponseCachingKeyProvider.cs#L80-L83

Found by Linux Verification Center (linuxtesting.org) with SVACE.