patch 8.2.3914: various spelling mistakes in comments

Problem:    Various spelling mistakes in comments.
Solution:   Fix the mistakes. (Dominique Pellé, closes #9416)
diff --git a/src/gui_gtk.c b/src/gui_gtk.c
index 2ea7a5e..08290a5 100644
--- a/src/gui_gtk.c
+++ b/src/gui_gtk.c
@@ -2242,7 +2242,7 @@
 	gtk_window_present(GTK_WINDOW(frdp->dialog));
 
 	// For :promptfind dialog, always give keyboard focus to 'what' entry.
-	// For :promptrepl dialog, give it to 'with' entry if 'what' has an
+	// For :promptrepl dialog, give it to 'with' entry if 'what' has a
 	// non-empty entry; otherwise, to 'what' entry.
 	gtk_widget_grab_focus(frdp->what);
 	if (do_replace && entry_get_text_length(GTK_ENTRY(frdp->what)) > 0)