Update dependency docker/buildx to v0.28.0

[renovate]

This PR contains the following updates:

Package	Update	Change
docker/buildx	minor	v0.27.0 -> v0.28.0

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Release Notes

docker/buildx (docker/buildx)

v0.28.0

Compare Source

Welcome to the v0.28.0 release of buildx!

Please try out the release binaries and report any issues at
https://github.com/docker/buildx/issues.

Contributors

• Tõnis Tiigi
• CrazyMax
• Akihiro Suda
• Dan Duvall
• Jonathan A. Sternberg
• Sebastiaan van Stijn
• Will Nonnemaker

Notable Changes

• When building with Dockerfile 1.18.0+ frontend (BuildKit v0.24) you can now use new Git URLs with query options for build context and named contexts in build and bake command. More info moby/buildkit#6183
• Add formatting options to the buildx du command for custom and machine-readable output. #​3377
• Kubernetes driver now supports env.<key> driver opts. #​3373
• Add support for BUILDKIT_SYNTAX build argument when BuildKit has Dockerfile frontend disabled. #​3385
• Fix failing early when trying to export index annotations with moby exporter. #​3384
• Fix possible errors on Windows from symlink handling. #​3386

Dependency Changes

• github.com/cpuguy83/go-md2man/v2 v2.0.6 -> v2.0.7
• github.com/moby/buildkit 955c2b2 -> v0.24.0
• github.com/spf13/pflag v1.0.6 -> v1.0.7
• github.com/stretchr/testify v1.10.0 -> v1.11.0

Previous release can be found at v0.27.0

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