git: Add CHERRY_PICK_HEAD to the list of merge heads (#26145)

Attempt to fix an issue where conflicts from a cherry-pick don't get
cleared out of the git panel after being resolved.

Release Notes:

- Git Beta: Fixed resolution of conflicts from cherry-picks not being
reflected in the git panel

crates/git/src/repository.rs

@@ -427,6 +427,15 @@ impl GitRepository for RealGitRepository {
                 true
             })
             .ok();
+        if let Some(oid) = self
+            .repository
+            .lock()
+            .find_reference("CHERRY_PICK_HEAD")
+            .ok()
+            .and_then(|reference| reference.target())
+        {
+            shas.push(oid.to_string())
+        }
         shas
     }