chore(deps): update module github.com/bufbuild/buf/cmd/buf to v1.68.3 (main) (#15138)

This PR contains the following updates:

| Package | Change |
[Age](https://docs.renovatebot.com/merge-confidence/) |
[Confidence](https://docs.renovatebot.com/merge-confidence/) |
|---|---|---|---|
|
[github.com/bufbuild/buf/cmd/buf](https://redirect.github.com/bufbuild/buf)
| `v1.68.2` → `v1.68.3` |
![age](https://developer.mend.io/api/mc/badges/age/go/github.com%2fbufbuild%2fbuf%2fcmd%2fbuf/v1.68.3?slim=true)
|
![confidence](https://developer.mend.io/api/mc/badges/confidence/go/github.com%2fbufbuild%2fbuf%2fcmd%2fbuf/v1.68.2/v1.68.3?slim=true)
|

---

> [!WARNING]
> Some dependencies could not be looked up. Check the warning logs for
more information.

---

### Release Notes

<details>
<summary>bufbuild/buf (github.com/bufbuild/buf/cmd/buf)</summary>

###
[`v1.68.3`](https://redirect.github.com/bufbuild/buf/blob/HEAD/CHANGELOG.md#v1683---2026-04-20)

[Compare
Source](https://redirect.github.com/bufbuild/buf/compare/v1.68.2...v1.68.3)

- Fix `buf format` error handling for edition 2024.

</details>

---

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk patch-level tooling update affecting protobuf
formatting/linting behavior in CI/build containers, with no runtime code
changes.
> 
> **Overview**
> Updates the build tooling to use `github.com/bufbuild/buf/cmd/buf`
`v1.68.3` (from `v1.68.2`) in `mimir-build-image/Dockerfile`.
> 
> Adjusts `Makefile`’s `LATEST_BUILD_IMAGE_TAG` to point to the newly
built `mimir-build-image` containing this dependency bump.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
c2e7495. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Signed-off-by: renovate-sh-app[bot] <219655108+renovate-sh-app[bot]@users.noreply.github.com>
Co-authored-by: renovate-sh-app[bot] <219655108+renovate-sh-app[bot]@users.noreply.github.com>
Co-authored-by: mimir-github-bot[bot] <199097951+mimir-github-bot[bot]@users.noreply.github.com>

Author: renovate-sh-app[bot]

Makefile

@@ -224,7 +224,7 @@ mimir-build-image/$(UPTODATE): mimir-build-image/*
 # All the boiler plate for building golang follows:
 SUDO := $(shell docker info >/dev/null 2>&1 || echo "sudo -E")
 BUILD_IN_CONTAINER ?= true
-LATEST_BUILD_IMAGE_TAG ?= pr15120-d07f30bfa3
+LATEST_BUILD_IMAGE_TAG ?= pr15138-0634ad4d2f
 
 # TTY is parameterized to allow CI and scripts to run builds,
 # as it currently disallows TTY devices.

mimir-build-image/Dockerfile

@@ -58,7 +58,7 @@ RUN GO111MODULE=on \
 	go install github.com/norwoodj/helm-docs/cmd/helm-docs@v1.14.2 && \
 	go install github.com/open-policy-agent/conftest@v0.68.2 && \
 	go install github.com/uber-go/gopatch@v0.4.0 && \
-	go install github.com/bufbuild/buf/cmd/buf@v1.68.2 && \
+	go install github.com/bufbuild/buf/cmd/buf@v1.68.3 && \
 	rm -rf /go/pkg /go/src /root/.cache
 
 COPY --from=helm /usr/bin/helm /usr/bin/helm