`change_column_default` should be executed after type changing

If do not execute a type changing first, filling in default value may be
failed.

```
% ARCONN=postgresql be ruby -w -Itest test/cases/migration/compatibility_test.rb -n test_legacy_change_column_with_null_executes_update
Using postgresql
Run options: -n test_legacy_change_column_with_null_executes_update --seed 20459

E

Error:
ActiveRecord::Migration::CompatibilityTest#test_legacy_change_column_with_null_executes_update:
StandardError: An error has occurred, this and all later migrations canceled:

PG::StringDataRightTruncation: ERROR:  value too long for type character varying(5)
: UPDATE "testings" SET "foo"='foobar' WHERE "foo" IS NULL
```

1 files changed, 2 insertions, 2 deletions

diff --git a/activerecord/test/cases/migration/compatibility_test.rb b/activerecord/test/cases/migration/compatibility_test.rb
index e6ca252369..cc2391f349 100644
--- a/activerecord/test/cases/migration/compatibility_test.rb
+++ b/activerecord/test/cases/migration/compatibility_test.rb
@@ -16,7 +16,7 @@ module ActiveRecord
         ActiveRecord::Migration.verbose = false
 
         connection.create_table :testings do |t|
-          t.column :foo, :string, limit: 100
+          t.column :foo, :string, limit: 5
           t.column :bar, :string, limit: 100
         end
       end
@@ -134,7 +134,7 @@ module ActiveRecord
         def test_legacy_change_column_with_null_executes_update
           migration = Class.new(ActiveRecord::Migration[5.1]) {
             def migrate(x)
-              change_column :testings, :foo, :string, null: false, default: "foobar"
+              change_column :testings, :foo, :string, limit: 10, null: false, default: "foobar"
             end
           }.new