patch 8.2.0156: various typos in source files and tests

Problem:    Various typos in source files and tests.
Solution:   Fix the typos. (Emir Sari, closes #5532)
diff --git a/src/gui.c b/src/gui.c
index eec89d5..f1c36f4 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -3420,7 +3420,7 @@
     if (oldval != NULL && gui.in_use)
     {
 	/*
-	 * Check if the menu's go from grey to non-grey or vise versa.
+	 * Check if the menus go from grey to non-grey or vice versa.
 	 */
 	grey_old = (vim_strchr(oldval, GO_GREY) != NULL);
 	grey_new = (vim_strchr(p_go, GO_GREY) != NULL);