test(plausible): psql -q in _register_site — -t does not suppress command tags

psql -tAc still prints INSERT/CREATE command tags (e.g. "INSERT 0 1"), so
_register_site asserted out == site against "INSERT 0 1\nsite" and both
event-tracking roundtrip tests failed on their very first run (build 237 —
the custom tier had never executed before; install always failed earlier).
-q suppresses the tags; verified against the recipe db container.

tests/plausible/functional/test_event_tracking.py

@@ -59,7 +59,7 @@ def _register_site(domain: str, site: str) -> None:
         f"SELECT domain FROM sites WHERE domain = '{site}';"
     )
     out = lifecycle.exec_in_app(
-        domain, ["psql", "-U", "plausible", "-d", "plausible", "-tAc", sql], service="db"
+        domain, ["psql", "-q", "-U", "plausible", "-d", "plausible", "-tAc", sql], service="db"
     ).strip()
     assert out == site, f"site {site!r} not registered in postgres (got {out!r})"