build: Update OpenFeature.sln

[askpt]

This PR

• This PR fixes an issue related to opening the project in VSCode.

Related Issues

See log output here:

Failed at 'Open a solution with environment service' (5ms) with error: Error: An item with the same key has already been added. Key: 90e7ead3-251e-4490-af78-e758e33518e5
Failed at 'Open a solution' (8ms) with error: SolutionOpenError: Run into errors while opening the solution: Error: An item with the same key has already been added. Key: 90e7ead3-251e-4490-af78-e758e33518e5
Failed to open solution SolutionOpenError: Run into errors while opening the solution: Error: An item with the same key has already been added. Key: 90e7ead3-251e-4490-af78-e758e33518e5

How to test

Just open VSCode and check it's working again.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (eba8848) 93.50% compared to head (7b48ccc) 93.50%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #202 +/- ## ======================================= Coverage 93.50% 93.50% ======================================= Files 23 23 Lines 954 954 Branches 105 105 ======================================= Hits 892 892 Misses 38 38 Partials 24 24 ```

:umbrella: View full report in Codecov by Sentry.
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[askpt]

I guess someone must have originally added this manually, then?

@askpt can you run these commands locally, and assuming they do what I expect, check in the results?

git reset @~ --hard
dotnet sln remove test/OpenFeature.E2ETests/OpenFeature.E2ETests.csproj
dotnet sln add test/OpenFeature.E2ETests/OpenFeature.E2ETests.csproj

Did this now. Please review again.