Remove bentoburr

[jernejfrank]

This might just me not being in the loop, but is this still relevant? It drags a lot of things into the release and I am not sure if it is still relevant since upstream is archived.

Changes

• removed the submodule (we are free of submodules now)
• removed the doc references pointing to it

How I tested this

Notes

The BentoBurr submodule pointed to an external example repo (github.com/bentoml/BentoBurr) that was archived read-only in August 2025, and the submodule itself was never initialized in practice — it existed only as a dangling reference that shipped as an empty directory plus a stale .gitmodules entry in the ASF source release tarball. The accompanying docs links were broken from the start, pointing to examples/deployment/aws/bentoml, a path that never existed in the repo. Since Burr has no code-level BentoML integration (the example lived entirely upstream), removing the submodule, .gitmodules, and the two doc mentions drops dead weight with no loss of functionality.

Checklist

• PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.