Bump pydocket minimum version to 0.17.7
Raises the lower bound from >=0.17.2 to >=0.17.7 to pick up critical fixes
for Prefect's execution_ttl=0 configuration:
- 0.17.6 (PR #331): Generation counter for Perpetual rescheduling races
- 0.17.7 (PR #335): Atomic _mark_as_terminal prevents execution_ttl=0
from deleting Perpetual successor state, which would silently kill all
Perpetual services (Foreman, Scheduler, Late Runs, etc.) after their
first execution
Closes #20729
Co-Authored-By: alex.s@prefect.io <ajstreed1@gmail.com>