Fix a bug introduced by previous bugfix

This commit fixes a bug but introduced another when completing a
symbol in xref-find-definitions.

commit ee58d92
Author: Michał Krzywkowski <k.michal@zoho.com>
Date:   Sun Nov 4 16:59:05 2018 +0100

* eglot.el (xref-backend-identifier-completion-table): Use vector.

lisp/progmodes/eglot.el

@@ -1374,7 +1374,7 @@ DUMMY is ignored."
                                     :position (plist-get
                                                (plist-get location :range)
                                                :start))
-                              :locations (list location)
+                              :locations (vector location)
                               :kind kind
                               :containerName containerName))
                 (jsonrpc-request server