patch 9.0.0883: a silent mapping may cause dots on the command line

Problem:    A silent mapping may cause dots on the command line.
Solution:   Don't show dots for completion if they are not going to be removed
            again. (closes #11501)
diff --git a/runtime/doc/map.txt b/runtime/doc/map.txt
index c33c9f8..494b629 100644
--- a/runtime/doc/map.txt
+++ b/runtime/doc/map.txt
@@ -234,6 +234,9 @@
 the executed command are still given though.  To shut them up too, add a
 ":silent" in the executed command: >
 	:map <silent> ,h :exe ":silent normal /Header\r"<CR>
+Note that the effect of a command might also be silenced, e.g., when the
+mapping selects another entry for command line completion it won't be
+displayed.
 Prompts will still be given, e.g., for inputdialog().
 Using "<silent>" for an abbreviation is possible, but will cause redrawing of
 the command line to fail.