fix: update return type

extensions/functions_geometry.yaml

@@ -145,26 +145,26 @@ scalar_functions:
       a negative `buffer_radius` will always return an emtpy geometry.
     impls:
       - args:
-          - value: geometry
-            name: geom
-          - value: fp64
-            name: buffer_radius
-        return: geometry
+          - name: geom
+            value: u!geometry
+          - name: buffer_radius
+            value: fp64
+        return: u!geometry
   -
     name: "centroid"
     description: >
       Return a point which is the geometric center of mass of the input geometry.
     impls:
       - args:
-          - value: geometry
-            name: geom
-        return: geometry
+          - name: geom
+            value: u!geometry
+        return: u!geometry
   -
     name: "minimum_bounding_circle"
     description: >
       Return the smallest circle polygon that contains the input geometry.
     impls:
       - args:
-          - value: geometry
-            name: geom
-        return: geometry
+          - name: geom
+            value: u!geometry
+        return: u!geometry