Clean up dev branches after release

[edoaltamura]

What should we add?

After the release of 0.8, clean up the branches used for specific PRs - only leave active ones such as the Pytorch connector one.

[edoaltamura]

• feature-predict_proba: @oscar-wallis could you please remind me whether this is linked to an issue? What do you think we should do next with this branch? An idea could be to include it at some point in the 0.8.x series.
• fix-608-Shape-mismatch-with-NeuralNetworkRegressor-+-SamplerQNN: @OkuyanBoga now that V2s are merged, do we still need this branch?
• main must be re-synced with the upstream main by resolving potential conflicts, otherwise we'll have trouble creating dev branches going forward.
• refractor-pytorch-pt2 and support-py313 are to be kept because they're linked to open issues.