Fix wrong xorm Delete usage (#27995)

## Bug in Gitea
I ran into this bug when I accidentally used the wrong redirect URL for
the oauth2 provider when using mssql. But the oauth2 provider still got
added.
Most of the time, we use `Delete(&some{id: some.id})` or
`In(condition).Delete(&some{})`, which specify the conditions. But the
function uses `Delete(source)` when `source.Cfg` is a `TEXT` field and
not empty. This will cause xorm `Delete` function not working in mssql.

https://github.com/go-gitea/gitea/blob/61ff91f9603806df2505907614b9006bf721b9c8/models/auth/source.go#L234-L240

## Reason
Because the `TEXT` field can not be compared in mssql, xorm doesn't
support it according to [this
PR](https://gitea.com/xorm/xorm/pulls/2062)
[related
code](https://gitea.com/xorm/xorm/src/commit/b23798dc987af776bec867f4537ca129fd66328e/internal/statements/statement.go#L552-L558)
in xorm
```go
if statement.dialect.URI().DBType == schemas.MSSQL && (col.SQLType.Name == schemas.Text ||
   col.SQLType.IsBlob() || col.SQLType.Name == schemas.TimeStampz) {
   if utils.IsValueZero(fieldValue) {
     continue
   }
   return nil, fmt.Errorf("column %s is a TEXT type with data %#v which cannot be as compare condition", col.Name, fieldValue.Interface())
   }
}
```
When using the `Delete` function in xorm, the non-empty fields will
auto-set as conditions(perhaps some special fields are not?). If `TEXT`
field is not empty, xorm will return an error. I only found this usage
after searching, but maybe there is something I missing.

---------

Co-authored-by: delvh <dev.lh@web.de>

models/auth/source.go

@@ -234,7 +234,7 @@ func CreateSource(ctx context.Context, source *Source) error {
 	err = registerableSource.RegisterSource()
 	if err != nil {
 		// remove the AuthSource in case of errors while registering configuration
-		if _, err := db.GetEngine(ctx).Delete(source); err != nil {
+		if _, err := db.GetEngine(ctx).ID(source.ID).Delete(new(Source)); err != nil {
 			log.Error("CreateSource: Error while wrapOpenIDConnectInitializeError: %v", err)
 		}
 	}