fix: Increase the parallelism config to fix flaky tests, revert bad commits (#13410)

The specs break only in Circle CI, we have to figure out the root cause
for the same. At the moment, I have increased the parallelism to fix
this.

db/migrate/20260130061021_add_index_to_reporting_events_for_response_distribution.rb

@@ -0,0 +1,11 @@
+class AddIndexToReportingEventsForResponseDistribution < ActiveRecord::Migration[7.1]
+  disable_ddl_transaction!
+
+  def change
+    add_index :reporting_events,
+              [:account_id, :name, :inbox_id, :created_at],
+              name: 'index_reporting_events_for_response_distribution',
+              algorithm: :concurrently,
+              if_not_exists: true
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2026_01_20_121402) do
+ActiveRecord::Schema[7.1].define(version: 2026_01_30_061021) do
   # These extensions should be enabled to support this database
   enable_extension "pg_stat_statements"
   enable_extension "pg_trgm"
@@ -1115,6 +1115,7 @@ ActiveRecord::Schema[7.1].define(version: 2026_01_20_121402) do
     t.datetime "event_start_time", precision: nil
     t.datetime "event_end_time", precision: nil
     t.index ["account_id", "name", "created_at"], name: "reporting_events__account_id__name__created_at"
+    t.index ["account_id", "name", "inbox_id", "created_at"], name: "index_reporting_events_for_response_distribution"
     t.index ["account_id"], name: "index_reporting_events_on_account_id"
     t.index ["conversation_id"], name: "index_reporting_events_on_conversation_id"
     t.index ["created_at"], name: "index_reporting_events_on_created_at"