chore(deps): update docker.io/library/golang docker tag to v1.26.1 (#47847)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| docker.io/library/golang | stage | minor | `1.25.8` → `1.26.1` |

---

### Configuration

📅 **Schedule**: Branch creation - "on saturday" (UTC), Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

---

This PR was generated by [Mend Renovate](https://mend.io/renovate/). View the [repository job log](https://developer.mend.io/github/DataDog/datadog-agent).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0My42Ni40IiwidXBkYXRlZEluVmVyIjoiNDMuNjYuNCIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOlsiY2hhbmdlbG9nL25vLWNoYW5nZWxvZyIsImRlcGVuZGVuY2llcyIsInFhL25vLWNvZGUtY2hhbmdlIl19-->


Co-authored-by: devflow.devflow-routing-intake <devflow.devflow-routing-intake@kubernetes.us1.ddbuild.io>

Author: renovate[bot]

test/fakeintake/Dockerfile

@@ -1,7 +1,7 @@
 ## Based on https://docs.docker.com/language/golang/build-images/
 # syntax=docker/dockerfile:1
 ARG BASE_IMAGE_REGISTRY=docker.io
-ARG GO_VERSION=1.25.8
+ARG GO_VERSION=1.26.1
 
 ## Build
 FROM ${BASE_IMAGE_REGISTRY}/library/golang:${GO_VERSION} AS build