Require array package to use current-line ()

Require array package to use current-line ()

The jsonrpc package (one of eglot's dependencies) recently
updated and removed the line requiring the array package. Since
current-line is provided by array and is used by eglot, require
array explicitly.

Here's jsonrpc's guilty commit:

https://git.savannah.gnu.org/cgit/emacs.git/commit/lisp/jsonrpc.el?id=c676444a43e4634c1f98ec286b5bd9e46b23216b

Copyright-paperwork-exempt: Yes

* eglot.el (array): Require it.

GitHub-reference: https://github.com/joaotavora/eglot/issues/294