ticdc: Removed error type detection in `CheckIsTiDB`

[hongyunyan]

Different downstreams will have different error messages for "select tidb_version()". We cannot provide a complete error whitelist in CheckIsTiDB.
Considering that we just want to know whether the downstream is tidb, the specific error cause is not very important. Therefore, we can directly output error information for all errors instead of returning errors.

[seiya-annie]

/found customer