ci: retrigger build after crypto_price_tracker doctest flake

The previous build run failed on an unrelated network-dependent
doctest in web_programming/crypto_price_tracker.py (1 failed, 3440
passed); all other checks (ruff, ty, sphinx, pre-commit.ci) passed.
Fork PRs cannot rerun failed jobs without admin rights, so push an
empty commit to retrigger the build.

Co-Authored-By: Claude Code <noreply@anthropic.com>

Author: xiao115255