test: Assert HttpOnly is unset on a minimal cookie

[anxkhn]

test_set_basic_cookie meant to check that a minimal cookie leaves HttpOnly
unset, but the assertion looked up the wrong attribute key:

assert not cookie.has_nonstandard_attr('httpOnpy')

'httpOnpy' is a typo (l -> p) for 'HttpOnly'. Cookies never carry the
misspelled key, so has_nonstandard_attr('httpOnpy') is always False and
assert not False passed unconditionally. The assertion therefore validated
nothing: a regression that wrongly set HttpOnly on a minimal cookie would not be
caught.

This corrects the key to 'HttpOnly', which is how the flag is actually stored and
read in src/crawlee/sessions/_cookies.py (rest={'HttpOnly': ''} when
http_only is set, read back via cookie.has_nonstandard_attr('HttpOnly')), and
matches the sibling assertion in test_set_cookie_with_all_attributes. The check
now genuinely asserts the minimal-cookie default.

-    assert not cookie.has_nonstandard_attr('httpOnpy')
+    assert not cookie.has_nonstandard_attr('HttpOnly')

Issues

• No related issue. Self-identified while reading the session-cookie tests.

Testing

• uv run pytest tests/unit/sessions/test_cookies.py - passes (8 passed).
• uv run pytest tests/unit/sessions/ - passes (30 passed).
• uv run poe lint - passes.
• uv run poe type-check - no new diagnostics from this change.
• Verified the assertion now has teeth: temporarily forcing the source to always
  set HttpOnly on minimal cookies makes the corrected assertion fail (red),
  whereas the old httpOnpy assertion still passed. On unmodified source it passes
  (green).

Checklist

• CI passed