Fix deprecated enum syntax in tests

activerecord/test/cases/adapters/abstract_mysql_adapter/mysql_enum_test.rb

@@ -11,7 +11,7 @@ class MySQLEnumTest < ActiveRecord::AbstractMysqlTestCase
   class EnumTest < ActiveRecord::Base
     attribute :state, :integer
 
-    enum state: {
+    enum :state, {
       start: 0,
       middle: 1,
       finish: 2

activerecord/test/cases/adapters/postgresql/enum_test.rb

@@ -11,12 +11,12 @@ class PostgresqlEnumTest < ActiveRecord::PostgreSQLTestCase
   class PostgresqlEnum < ActiveRecord::Base
     self.table_name = "postgresql_enums"
 
-    enum current_mood: {
+    enum :current_mood, {
       sad: "sad",
       okay: "ok", # different spelling
       happy: "happy",
       aliased_field: "happy"
-    }, _prefix: true
+    }, prefix: true
   end
 
   def setup