Fix typo in State trait rustdoc
/// IDs, which define a checkpoint in the state. Keys that exist under one state ID are not
/// required to be available under another. How this is handled is left up to the implementation.
///
-/// For example, a `State` defined over a merkle database would proved the root merkle hash as its
+/// For example, a `State` defined over a merkle database would prove the root merkle hash as its
/// state ID.
///
/// Available with the feature `"state-trait"` enabled.
