Minor: Re-enable Discussions (#7288)

* enable duscussions

* add mail target for issues

Author: assignUser

.asf.yaml

@@ -22,6 +22,7 @@ notifications:
   commits:      [email protected]
   issues:       [email protected]
   pullrequests: [email protected]
+  discussions: [email protected]
   jira_options: link label worklog
 github:
   description: "Official Rust implementation of Apache Arrow"
@@ -37,6 +38,7 @@ github:
     rebase: false
   features:
     issues: true
+    discussions: true
   protected_branches:
     main:
       required_status_checks: