Add changelog entry

.changelog/unreleased/breaking-changes/1446-fix-prost-version.md

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+- `[tendermint]` Bump `prost` and `prost-types` to their latest versions in tendermint crate.
+  This was missed in [#1444](https://github.com/informalsystems/tendermint-rs/pull/1444),
+  which only updated the two dependencies in `tendermint-rpc`, leading to duplicate versions
+  of both crates to be present in the dependency graph.
+  ([#1446](https://github.com/informalsystems/tendermint-rs/pull/1446))