fix(python): generate the instructor-latest tox environment for the canary

[feiiiiii5]

Description

python/tox.ini declared py3{10,12}-ci-instructor without its -latest sibling, while the instructor-latest install factor exists at python/tox.ini:217. Since .github/workflows/python-cron.yaml selects canary environments with tox -l | egrep -e '-latest$', no instructor -latest environment was ever generated and instructor version bumps were never exercised by the canary.

This adds the missing leg, keeping instructor's existing Python pair, so the envlist line matches the form used by every sibling package:

  py3{10,12}-ci-{instructor,instructor-latest}

Resolves #3799

Verification

From python/, before the change:

$ tox -l | grep instructor
py310-ci-instructor
py312-ci-instructor
$ tox -l | wc -l          # 149
$ tox -l | egrep -c -e '-latest$'   # 69

After the change:

$ tox -l | grep instructor
py310-ci-instructor
py310-ci-instructor-latest
py312-ci-instructor
py312-ci-instructor-latest
$ tox -l | wc -l          # 151
$ tox -l | egrep -c -e '-latest$'   # 71

tox -l was run with tox 4.56.4. No test code changed, so no suite result is claimed here; the change only makes the existing instructor-latest factor reachable. python/scripts/select_tox_environments.py matches instrumentors against whole dash-delimited segments of the environment name, so both new environments still resolve to the instructor package during pull-request selection.

Checklist:

• Follows OpenInference configuration to hide sensitive info - not applicable, no span attributes are produced by this change
• Spans properly inherit from context attributes - not applicable
• Properly respects suppress tracing context - not applicable

Note on authorship

Produced by an AI agent under this account owner's direction; the tox -l outputs above are its own local runs. No human has reviewed the diff yet.