Fix deprecation warnings in spec/services/issues/bulk_update_service_spec.rb

Signed-off-by: Rémy Coutable <remy@rymai.me>

spec/services/issues/bulk_update_service_spec.rb

@@ -18,7 +18,7 @@ describe Issues::BulkUpdateService, services: true do
       @issues = create_list(:issue, 5, project: @project)
       @params = {
         state_event: 'close',
-        issues_ids: @issues.map(&:id)
+        issues_ids: @issues.map(&:id).join(",")
       }
     end
 
@@ -38,7 +38,7 @@ describe Issues::BulkUpdateService, services: true do
       @issues = create_list(:closed_issue, 5, project: @project)
       @params = {
         state_event: 'reopen',
-        issues_ids: @issues.map(&:id)
+        issues_ids: @issues.map(&:id).join(",")
       }
     end
 
@@ -58,7 +58,7 @@ describe Issues::BulkUpdateService, services: true do
     before do
       @new_assignee = create :user
       @params = {
-        issues_ids: [issue.id],
+        issues_ids: issue.id.to_s,
         assignee_id: @new_assignee.id
       }
     end
@@ -97,7 +97,7 @@ describe Issues::BulkUpdateService, services: true do
     before do
       @milestone = create(:milestone, project: @project)
       @params = {
-        issues_ids: [issue.id],
+        issues_ids: issue.id.to_s,
         milestone_id: @milestone.id
       }
     end