chore: enforce missing_docs from the workspace manifest

One [workspace.lints.rust] table replaces the deny attribute
scattered across every lib.rs, and each crate opts in through
[lints]. The lint now also reaches the integration-test crates,
whose roots gain their one-line docs.

integrations/rhema-forge-integration/src/lib.rs

@@ -46,7 +46,6 @@
 //!   dispatches, surfaces, and drops
 
 #![forbid(unsafe_code)]
-#![deny(missing_docs)]
 
 pub mod error;
 pub mod event;