Remove unnecessary option

Was overseen in 47512f7

tests/precice-adapter-config.json

@@ -5,6 +5,5 @@
       "coupling_mesh_name": "Dummy-Mesh",
       "write_data_name": "Dummy-Write",
       "read_data_name": "Dummy-Read",
-      "interpolation_type": "rbf_segregated"
     }
-}
+}