chore: Update default branch to track 2.72.0 / 26.08

[mc-nv]

^{CI (internal): [#57176507](http://tritonserver.local/ci/pipelines/57176507)}

What does the PR do?

Advances main to track the next development release now that the current train is at code freeze. Bumps the Triton version and container version:

• TRITON_VERSION: 2.71.0dev → 2.72.0dev
• build.py DEFAULT_TRITON_VERSION_MAP: release_version → 2.72.0dev, triton_container_version → 26.08dev

Checklist

• PR title reflects the change and is of format <commit_type>: <Title>
• Changes are described in the pull request.
• Related issues are referenced.
• Populated github labels field
• Added test plan and verified test passes.
• Verified that the PR passes existing CI.
• Verified copyright is correct on all changed files.
• Added succinct git squash message before merging.
• All template sections are filled out.

Commit Type:

Uses chore (mechanical version-tracking bump; not in the list below).

• build

Related PRs:

triton-inference-server/model_analyzer#1028

Where should the reviewer start?

TRITON_VERSION and the DEFAULT_TRITON_VERSION_MAP block in build.py.

Test plan:

Version-string-only change; validated by the standard CI build.

• CI Pipeline ID: 57176507

Caveats:

None — mechanical version bump.

Background

Routine code-freeze step: once a release branch is cut, main advances to the next dev version so post-freeze work targets the upcoming train.

Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)

• Resolves: TRI-1544