Bug due to 'unverified_providers ' in DSSE Verify

[Yaxhveer]

I have encountered a bug related to the assignment unverified_providers := ev.providers here. The unverified_providers and ev.proviers both refer to the same underlying array. Later the verified key are removed from unverified_providers, here, but since the capacity of the array is still greater than length of unverified_providers, golang reuses the same underlying array instead of creating new one. This therefore modify the value of ev.Provider and remove the verified keys.