Cleanup: Dead code _check_step_dependencies in orchestration/workflow_executor.py

[mrveiss]

Problem

WorkflowExecutor._check_step_dependencies() at orchestration/workflow_executor.py:248-275 is now dead code. It was the per-step dependency check used by the old sequential execution loop, which was replaced in PR #2197 with _group_steps_by_dependency() (topological sort that handles dependencies at the group level).

Evidence

# Only callers of _check_step_dependencies:
grep -rn "_check_step_dependencies" autobot-backend/orchestration/
# Result: only the definition at line 248 — no callers

# The OLD call site was in execute_coordinated_workflow:
#   for step in steps:
#       if not await self._check_step_dependencies(step, ...):
# This was replaced by:
#   groups = self._group_steps_by_dependency(steps)
#   for group in groups:
#       await self._execute_step_group(group, ...)

Note: services/workflow_automation/executor.py has its OWN separate _check_step_dependencies — that one IS still called and is unrelated.

Impact

Low — Dead code, no functional impact. Adds confusion about which dependency checking method is active.

Expected Fix

Remove _check_step_dependencies from orchestration/workflow_executor.py (lines 248-275). The services/workflow_automation/executor.py version is separate and unaffected.

Discovered During

Implementation of #2172 (parallel step execution replaced the sequential loop that called this method).