Fix some bug on migrations (#30647)

Fix https://github.com/go-gitea/gitea/pull/23894#discussion_r1573718690

models/migrations/v1_16/v210.go

@@ -43,11 +43,6 @@ func RemigrateU2FCredentials(x *xorm.Engine) error {
 		if err != nil {
 			return err
 		}
-	case schemas.ORACLE:
-		_, err := x.Exec("ALTER TABLE webauthn_credential MODIFY credential_id VARCHAR(410)")
-		if err != nil {
-			return err
-		}
 	case schemas.MSSQL:
 		// This column has an index on it. I could write all of the code to attempt to change the index OR
 		// I could just use recreate table.

models/migrations/v1_22/v286.go

@@ -53,7 +53,7 @@ func expandHashReferencesToSha256(x *xorm.Engine) error {
 			if setting.Database.Type.IsMySQL() {
 				_, err = db.Exec(fmt.Sprintf("ALTER TABLE `%s` MODIFY COLUMN `%s` VARCHAR(64)", alts[0], alts[1]))
 			} else if setting.Database.Type.IsMSSQL() {
-				_, err = db.Exec(fmt.Sprintf("ALTER TABLE [%s] ALTER COLUMN [%s] VARCHAR(64)", alts[0], alts[1]))
+				_, err = db.Exec(fmt.Sprintf("ALTER TABLE [%s] ALTER COLUMN [%s] NVARCHAR(64)", alts[0], alts[1]))
 			} else {
 				_, err = db.Exec(fmt.Sprintf("ALTER TABLE `%s` ALTER COLUMN `%s` TYPE VARCHAR(64)", alts[0], alts[1]))
 			}