Fix some meta.license attributes

pkgs/applications/editors/emacs-modes/erlang/default.nix

···
   meta = with stdenv.lib; {
     homepage = "http://github.com/erlang/otp";
     description = "Erlang mode for Emacs";
-    licence = licenses.asl20;
+    license = licenses.asl20;
     platforms = platforms.unix;
     maintainers = [ maintainers.samuelrivas ];
   };

pkgs/top-level/python-packages.nix

···
     meta = {
       description = "Minimal task scheduling abstraction";
       homepage = "http://github.com/ContinuumIO/dask/";
-      licenses = licenses.bsd3;
+      license = licenses.bsd3;
       maintainers = with maintainers; [ fridh ];
     };
   };
···
     meta = {
       description = "Easy to use python subprocess interface";
       homepage = "https://github.com/ponty/EasyProcess";
-      licenses = licenses.bsdOriginal;
+      license = licenses.bsdOriginal;
       maintainers = with maintainers; [ layus ];
     };
   };