Fixs todos in migration file (#3379)

storage/sql_migrations/003_did.sql

@@ -16,10 +16,10 @@ create table did_document_version
     -- id is v4 uuid
     id varchar(36) not null primary key,
     did varchar(370) not null,
-    created_at integer, -- make not nil in future PR
-    updated_at integer, -- make not nil in future PR
+    created_at integer not null,
+    updated_at integer not null,
     version int not null,
-    raw $TEXT_TYPE, -- make not nil in future PR
+    raw $TEXT_TYPE not null,
     unique (did, version),
     foreign key (did) references did (id) on delete cascade
 );
@@ -102,7 +102,9 @@ create table did_document_to_service
 );
 
 -- +goose Down
+drop table did_document_to_verification_method;
 drop table did_verification_method;
+drop table did_document_to_service;
 drop table did_service;
 drop table did_change_log;
 drop table did_document_version;