Changes

feat: update go1.25.8 toolchain pin for tiflow/ticdc unit jobs (#4376)

## Summary
This PR update image to mix Go patch toolchain artifacts (`go1.25.8` vs
older `go tool`) that cause compile failures in PR jobs.

## Why
Some jobs are still running in environments/images that are not fully
aligned to Go `1.25.8`, while repo-side changes already pull `1.25.8`
artifacts. This can trigger errors like:

```text
compile: version "go1.25.8" does not match go tool version "go1.25.x"
```
## replay test

https://github.com/pingcap/ticdc/pull/4467

-
https://prow.tidb.net/view/gs/prow-tidb-logs/pr-logs/pull/pingcap_ticdc/4467/pull-unit-test/2034863608625631232
-
https://prow.tidb.net/view/gs/prow-tidb-logs/pr-logs/pull/pingcap_ticdc/4467/pull-unit-test/2034863608625631232

https://github.com/pingcap/tiflow/pull/12560

-
https://prow.tidb.net/view/gs/prow-tidb-logs/pr-logs/pull/pingcap_tiflow/12560/pull-unit-test-cdc/2034866305454051328
-
https://do.pingcap.net/jenkins/blue/organizations/jenkins/pingcap%2Ftiflow%2Fghpr_verify/detail/ghpr_verify/4500/pipeline/

Signed-off-by: lyb <yebin.li@pingcap.com>
 (commit: 2572069)