patch 9.0.0004: plural messages not translated properly

Problem:    Plural messages not translated properly.
Solution:   Use ngettext() in a few more places. (Matvey Tarasov,
            closes #10606)
diff --git a/src/version.c b/src/version.c
index 2faf3bd..dd99f85 100644
--- a/src/version.c
+++ b/src/version.c
@@ -736,6 +736,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4,
+/**/
     3,
 /**/
     2,