Drop trivial regression tests from nldi cleanup

The trim_start drop, falsy-zero (lat/long/comid), and unbalanced-quote
fixes are each one-line changes whose regressions are obvious on read.
The remaining three tests (search-without-nav-mode crash, ValueError vs
TypeError, and lowercase normalization) cover behavior that's less
self-evident from the code.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: thodson-usgs

tests/nldi_test.py

@@ -302,56 +302,3 @@ def test_validate_navigation_mode_raises_value_error_for_invalid():
 def test_validate_navigation_mode_normalizes_lowercase():
     """Regression: lowercase values used to validate but be sent unchanged."""
     assert _validate_navigation_mode("um") == "UM"
-
-
-def test_get_flowlines_by_comid_includes_trim_start(requests_mock):
-    """Regression: trim_start was previously dropped on the comid code path."""
-    request_url = f"{NLDI_API_BASE_URL}/comid/13294314/navigation/UM/flowlines"
-    response_file_path = "tests/data/nldi_get_flowlines_by_comid.json"
-    mock_request(requests_mock, request_url, response_file_path)
-
-    get_flowlines(navigation_mode="UM", comid=13294314, trim_start=True)
-
-    sent = requests_mock.request_history[-1]
-    assert sent.qs.get("trimstart") == ["true"]
-
-
-def test_get_features_with_zero_coordinates(requests_mock):
-    """Regression: lat=0.0 / long=0.0 were treated as missing (falsy bug)."""
-    request_url = f"{NLDI_API_BASE_URL}/comid/position"
-    requests_mock.get(
-        request_url,
-        json={"type": "FeatureCollection", "features": []},
-        headers={"mock_header": "value"},
-    )
-
-    gdf = get_features(lat=0.0, long=0.0, as_json=True)
-    assert isinstance(gdf, dict)
-    sent = requests_mock.request_history[-1]
-    assert "POINT(0.0 0.0)" in sent.qs.get("coords", [""])[0].upper()
-
-
-def test_get_features_lat_zero_long_missing_raises():
-    """Regression: lat=0.0 with missing long was silently accepted (falsy bug)."""
-    with pytest.raises(ValueError, match="Both lat and long are required"):
-        get_features(lat=0.0)
-
-
-def test_get_features_error_message_has_balanced_quotes(requests_mock):
-    """Regression: error message had a missing closing quote after feature_id."""
-    request_url = f"{NLDI_API_BASE_URL}/WQP/USGS-bad/navigation/UM/nwissite"
-    # Use a status code utils.query() doesn't intercept so the _query_nldi
-    # error path runs and we see its formatted message.
-    requests_mock.get(request_url, status_code=403, reason="Forbidden", json={})
-    mock_request_data_sources(requests_mock)
-
-    with pytest.raises(ValueError) as exc:
-        get_features(
-            feature_source="WQP",
-            feature_id="USGS-bad",
-            data_source="nwissite",
-            navigation_mode="UM",
-        )
-    msg = str(exc.value)
-    # Closing quote after feature_id must now be present.
-    assert "feature_id 'USGS-bad'," in msg