Use poetry-core instead of poetry

This may unblock release 0.49.0, because it may provide Poetry 1.2
already, which is needed for serving dependency groups, which got
recently introduced into `pyproject.toml` of Wetterdienst.

recipe/meta.yaml

@@ -21,7 +21,7 @@ requirements:
   host:
     - python >=3.7
     - pip
-    - poetry
+    - poetry-core
   run:
     - python >=3.7
     - pandas