This fixes the following compile warning when lisp files are
compiled together by:
emacs ... -batch -f batch-byte-compile lisp/*.el
This is the warning:
In end of data:
lisp/ein-notebooklist.el:397:1:Warning: the function `ein:default-url-or-port'
might not be defined at runtime.
I don't know why this warning occurs, but as the line removed is
not needed any more, this is an OK change.