test: mark test_infinite_scroll_on_dynamic_page as flaky

[vdusek]

test_infinite_scroll_on_dynamic_page intermittently fails on the windows-latest unit-test job. Under pytest-xdist load the Windows runner transiently runs out of socket buffer space (WSAENOBUFS), so page.goto to the local test server fails with net::ERR_NO_BUFFER_SPACE. The failure happens during navigation setup, before infinite_scroll (the code under test) ever runs, so it's an environmental flake rather than a product or test-logic defect.

This mirrors the repo's established convention for the same signature (test_browser_pool.py, test_stagehand_browser_controller.py, test_adaptive_playwright_crawler.py): mark the test with @pytest.mark.flaky(reruns=3, reason=...). The test's assertions stay deterministic given a successful navigation, so a real regression still fails all attempts; the reruns only absorb transient connection failures.

Failing run: https://github.com/apify/crawlee-python/actions/runs/29315899194/job/87029744185

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.32%. Comparing base (e846690) to head (b46190a).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2072      +/-   ##
==========================================
- Coverage   93.34%   93.32%   -0.03%     
==========================================
  Files         179      179              
  Lines       12496    12496              
==========================================
- Hits        11665    11662       -3     
- Misses        831      834       +3     

Flag	Coverage Δ
unit	93.32% <ø> (-0.03%)	⬇️

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