Update templates for 3.1

[ryanbrandenburg]

Fixes #14486.

[mkArtakMSFT]

@aspnet/build folks,I assume the <TargetFramework> in the change in .csproj files will happen as part of rebranding work? Currently it's defined as below:

<TargetFramework>${DefaultNetCoreTargetFramework}</TargetFramework>

[mkArtakMSFT]

Thanks for quickly handling this, @ryanbrandenburg.
Let's get this merged after getting confirmation from the Build folks first.

[wtgodbe]

I assume the in the change in .csproj files will happen as part of rebranding work?

Yes, it should just get the right value from root dir.build.props:
https://github.com/aspnet/AspNetCore/blob/release/3.1/Directory.Build.props#L55

[dougbu]

it should just get the right value from root dir.build.props

And, the value is correct in every branch 😺

[dougbu]

@ryanbrandenburg please also update 'master' to use 5.0 identities and perhaps a still-higher precedence

[ryanbrandenburg]

Closing in favor of #14637 which uses the new branch.