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GH-36863: [C#][Packaging] Do not shutdown PythonEngine on CDataInterfacePythonTests if .NET is > 5.0 (#36868)

### Rationale for this change

Tests are failing on maintenance branch to generate Nuget packages. This has been tested on the maintenance branch and it solves the issue.

### What changes are included in this PR?

Only Shutdown if `#if !NET5_0_OR_GREATER`

### Are these changes tested?

Locally and via archery.

### Are there any user-facing changes?

No
* Closes: #36863

Authored-by: Raúl Cumplido <raulcumplido@gmail.com>
Signed-off-by: Raúl Cumplido <raulcumplido@gmail.com>