Fix warning for dynamic trait objects

[amanusk]

Fix trait objects without an explicit dyn are deprecated warning

Starting rust stable version 1.37.0, the old syntax for trait object emits errors.
Similarly, the updated protobuf version generates files adhering to the new standard.

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• Bump Tendermint & ABCI version in README.md if version was updated

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[tomtau]

@amanusk thank you for your contribution!
The changes look good to me, but could you open the PR against the 'develop' branch: https://github.com/tendermint/rust-abci/tree/develop ? We'll make a release from it later