Remove System.Memory dependency from net 6+

[thompson-tomo]

Is your feature request related to a problem? Please describe.
I want to minimise dependencies in my project by utilising framework dependencies wherever possible

Describe the solution you'd like
I want the package to not have an explicit dependency on System.Memory on net 6+.

Describe alternatives you've considered
Accept the additional dependency

Additional context
n/

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Please upvote 👍 this issue if you are interested in it.

[patriksvensson]

@thompson-tomo Spectre.Console does not have a dependency on System.Memory on net6.0. It has a conditional dependency on that package for netstandard2.0.

[thompson-tomo]

Ahh, I had not checked the preview packages and only looked at the release versions.

[patriksvensson]

Hmm, we might actually need to investigate this. Seems like packaging doesn't respect the target framework condition for some reason: https://www.nuget.org/packages/Spectre.Console/

[thompson-tomo]

Closing this as it is now not being included.