[stable2407] Backport #6031 (#6106)

Backport #6031 into `stable2407` from drewstone.

See the
[documentation](https://github.com/paritytech/polkadot-sdk/blob/master/docs/BACKPORT.md)
on how to use this bot.

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Co-authored-by: drewstone <drewstone329@gmail.com>
Co-authored-by: Egor_P <egor@parity.io>

bridges/primitives/header-chain/src/justification/verification/equivocation.rs

@@ -34,6 +34,8 @@ use sp_runtime::traits::Header as HeaderT;
 use sp_std::{
 	collections::{btree_map::BTreeMap, btree_set::BTreeSet},
 	prelude::*,
+	vec,
+	vec::Vec,
 };
 
 enum AuthorityVotes<Header: HeaderT> {

bridges/primitives/header-chain/src/justification/verification/mod.rs

@@ -35,6 +35,8 @@ use sp_std::{
 		btree_set::BTreeSet,
 	},
 	prelude::*,
+	vec,
+	vec::Vec,
 };
 
 type SignedPrecommit<Header> = finality_grandpa::SignedPrecommit<

bridges/primitives/header-chain/src/justification/verification/optimizer.rs

@@ -26,7 +26,7 @@ use crate::justification::verification::{
 };
 use sp_consensus_grandpa::AuthorityId;
 use sp_runtime::traits::Header as HeaderT;
-use sp_std::{collections::btree_set::BTreeSet, prelude::*};
+use sp_std::{collections::btree_set::BTreeSet, prelude::*, vec, vec::Vec};
 
 // Verification callbacks for justification optimization.
 struct JustificationOptimizer<Header: HeaderT> {

prdoc/pr_6031.prdoc

+title: "Import vec to bridges/primitives/header-chain"
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      Add the `vec` dependency to these files to resolve compiler errors.
+
+crates:
+  - name: bp-header-chain
+    bump: patch