Update System.Text.Json dependency

[WeihanLi]

• Fix the condition
• Remove System.Text.Json dependency for .NET 6, still required for .NET 5 because of new json features introduced in 6.0.0

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[tg123]

The library is built-in as part of the shared framework for .NET Core 3.0 and later versions
https://docs.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-overview?pivots=dotnet-5-0#how-to-get-the-library

[WeihanLi]

The library is built-in as part of the shared framework for .NET Core 3.0 and later versions
https://docs.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-overview?pivots=dotnet-5-0#how-to-get-the-library

The build would fail if remove the dependency for .NET 5, the built-in version seemed is not latest version

[tg123]

tests proj targets net5 as well, could you please elaborate yours

[WeihanLi]

The condition did not work before because of the condition typo

- Coondition
+ Condition

And it can be verified from the NuGet package dependencies

[tg123]

lol this is very interesting.
the coondition here was intent to make net5+ use their own builtin json library instead of a dependency
it equals to no condition today

i tested fixing the typo and found serval build errors and understand the issue eventually.

the correct way, i believe, to fix it is to fix the typo and workaround those features in .6
OR
change to condition to ==netstandard2.1 or ==net5 in case of adopting net7

seems the second one is easier as netcore3.1 and net5 are approaching the eol

[tg123]

thanks for the PR

/LGTM