build(deps): bump moby/buildkit from v0.26.3 to v0.29.0 in /ci

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: phlax <454682+phlax@users.noreply.github.com>

Author: 2 people

ci/Dockerfile-buildkit

@@ -1,3 +1,3 @@
 # We dont build from this dockerfile - we just parse the version, but storing
 # here means we get the dependabot updates
-FROM moby/buildkit:v0.26.3
+FROM moby/buildkit:v0.29.0