Bench(fix[lgtm]): Skip the optional-dependency tests on what they import

why: Both tests guard on `opentelemetry`, but that namespace package arrives
transitively, so the guard passes wherever libtmux is installed. What the
modules under test actually import is `opentelemetry.sdk`, the OTLP
exporters, and rampa, all of which ship only in the optional `otel` group --
which CI does not install. The guard therefore never fired and the tests
failed on import instead of skipping, which was the stated intent.

what:
- Guard on `opentelemetry.sdk` rather than the namespace package
- Guard the load scenario on rampa as well, since it imports both

Verified in both directions: without the group the two skip, and with it
installed they still run and pass rather than being silently disabled.

Author: tony

tests/test_lgtm_dashboards.py

@@ -277,7 +277,11 @@ def test_telemetry_doctests_execute() -> None:
     """
     import doctest
 
-    pytest.importorskip("opentelemetry", reason="otel dependency group not installed")
+    # The namespace package arrives transitively; the SDK is what this module
+    # actually imports, and it only ships in the optional group.
+    pytest.importorskip(
+        "opentelemetry.sdk", reason="otel dependency group not installed"
+    )
 
     spec = importlib.util.spec_from_file_location("telemetry", _LGTM / "telemetry.py")
     assert spec is not None
@@ -463,7 +467,10 @@ def test_a_failing_load_setup_is_attempted_once(
     input into thousands of servers and enough threads to saturate the machine.
     It did exactly that once, which is why this is pinned.
     """
-    pytest.importorskip("opentelemetry", reason="otel dependency group not installed")
+    pytest.importorskip(
+        "opentelemetry.sdk", reason="otel dependency group not installed"
+    )
+    pytest.importorskip("rampa", reason="otel dependency group not installed")
 
     monkeypatch.syspath_prepend(str(_LGTM))
     spec = importlib.util.spec_from_file_location("load_tmux", _LGTM / "load_tmux.py")