style: normalise blank lines between definitions

- two between top-level definitions, one between methods, none doubled inside a body

tests/test_social_lookahead.py

@@ -172,7 +172,6 @@ def test_reddit_live_empty_feed_is_a_real_absence(monkeypatch):
     assert "unavailable" not in out
 
 
-
 @pytest.mark.unit
 def test_stocktwits_empty_stream_for_a_past_window_is_unavailable(monkeypatch):
     monkeypatch.setattr(stocktwits, "urlopen", lambda *a, **k: _JsonResp({"messages": []}))
@@ -180,7 +179,6 @@ def test_stocktwits_empty_stream_for_a_past_window_is_unavailable(monkeypatch):
     assert "unavailable" in out and "not an absence" in out
 
 
-
 @pytest.mark.unit
 def test_reddit_window_straddling_the_lookback_is_unavailable(monkeypatch):
     # Ten days ago through five days ago: the week-long search never reaches the