Exclude PET-CF on UM3

There is are CC cores defined for the UM3

resources/definitions/ultimaker3.def.json

@@ -18,6 +18,10 @@
             "generic_cffpa",
             "generic_gffcpe",
             "generic_gffpa",
+            "generic_petcf",
+            "ultimaker_petcf_black",
+            "ultimaker_petcf_blue",
+            "ultimaker_petcf_gray",
             "structur3d_dap100silicone"
         ],
         "firmware_update_info":