Remove foreign key constraints from anon blocks & mute rules

We do it this way on other tables. Rails validates these on its own anyway.

db/migrate/20220714211614_set_on_delete_for_anonymous_blocks.rb

@@ -3,8 +3,8 @@
 class SetOnDeleteForAnonymousBlocks < ActiveRecord::Migration[6.1]
   def change
     change_table :anonymous_blocks do |t|
-      t.foreign_key :users, on_delete: :cascade
-      t.foreign_key :questions, on_delete: :cascade
+      t.remove_foreign_key :users
+      t.remove_foreign_key :questions
     end
   end
 end

db/migrate/20220714212414_set_on_delete_for_mute_rules.rb

@@ -3,7 +3,7 @@
 class SetOnDeleteForMuteRules < ActiveRecord::Migration[6.1]
   def change
     change_table :mute_rules do |t|
-      t.foreign_key :users, on_delete: :cascade
+      t.remove_foreign_key :users
     end
   end
 end

db/schema.rb

@@ -324,8 +324,5 @@ ActiveRecord::Schema.define(version: 2022_07_14_212414) do
     t.index ["user_id"], name: "index_users_roles_on_user_id"
   end
 
-  add_foreign_key "anonymous_blocks", "questions", on_delete: :cascade
-  add_foreign_key "anonymous_blocks", "users", on_delete: :cascade
-  add_foreign_key "mute_rules", "users", on_delete: :cascade
   add_foreign_key "profiles", "users"
 end