patch 8.2.3219: :find searches non-existing directories

Problem:    :find searches non-existing directories.
Solution:   Check the path is not "..".  Update help. (Christian Brabandt,
            closes #8612, closes #8533)
diff --git a/runtime/doc/editing.txt b/runtime/doc/editing.txt
index 2331798..6bc245a 100644
--- a/runtime/doc/editing.txt
+++ b/runtime/doc/editing.txt
@@ -1749,6 +1749,12 @@
 	/u/user_x/work/include
 	/u/user_x/include
 
+<   Note: If your 'path' setting includes an non-existing directory, Vim will
+   skip the non-existing directory, but continues searching in the parent of
+   the non-existing directory if upwards searching is used.  E.g. when
+   searching "../include" and that doesn't exist, and upward searching is
+   used, also searches in "..".
+
 3) Combined up/downward search:
    If Vim's current path is /u/user_x/work/release and you do >
 	set path=**;/u/user_x