vue: change license to ecl20

found at https://vue.tufts.edu/faq

pkgs/applications/misc/vue/default.nix

···
     maintainers = with lib.maintainers; [ raskin ];
     platforms = with lib.platforms; linux;
     sourceProvenance = with lib.sourceTypes; [ binaryBytecode ];
-    license = lib.licenses.free; # Apache License fork, actually
+    license = lib.licenses.ecl20;
   };
 }