Target net10.0 in RepoTasks

[mthalman]

The changes made to RepoTasks in https://github.com/dotnet/aspnetcore/pull/58090/files#diff-976f8f3081f5ec8e8aacf560c64825479b33b0953bdc4dec82255c7cbe8d01d9 will need to be reverted. Specifically, net9.0 should be changed back to $(DefaultNetCoreTargetFramework). This can be done once a dependency on a .NET SDK is taken that has these changes: dotnet/sdk#43015.

Related to dotnet/sdk#44685

[ViktorHofer]

@wtgodbe can you please help with this? This involves updating the SDK in this repo to a recent build and reverting the change in RepoTasks.csproj as described above.

[wtgodbe]

Sure, we were finally able to upgrade to the net10.0 SDK yesterday - #59058