Do not kill notes buffer for one-file-per-note.

Until now, with the setting `one-file-per-note` for `ebib-notes-storage`, every
time the entry buffer is updated, the notes buffer is killed. This was mainly to
prevent dozens of notes buffers from staying alive in an Emacs session. However,
it leads to a problem with the setting `all` for `ebib-notes-show-note-method`,
as seen in Github issue #283.

We may decide to turn this into a user-configurable option if users are annoyed
by the many note buffers staying open.

ebib.el

@@ -699,12 +699,9 @@ not have an associated index buffer, create one and fill it."
 MATCH-STR is a regexp that will be highlighted when it occurs in
 the field contents."
   (when ebib--note-window
-    (if (window-live-p ebib--note-window)
-        (let ((buf (window-buffer ebib--note-window)))
-          (delete-window ebib--note-window)
-          (if (eq ebib-notes-storage 'one-file-per-note)
-              (kill-buffer buf))
-          (setq ebib--needs-update nil))) ; See below.
+    (when (window-live-p ebib--note-window)
+      (delete-window ebib--note-window)
+      (setq ebib--needs-update nil)) ; See below.
     (setq ebib--note-window nil))
   (with-current-ebib-buffer 'entry
     (let ((inhibit-read-only t)