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_xmebw.c b/src/gui_xmebw.c
index 3387fbe..7ffa6f3 100644
--- a/src/gui_xmebw.c
+++ b/src/gui_xmebw.c
@@ -970,7 +970,7 @@
     }
     else
     {
-	// FIXME: We should calculate an drawing offset for the pixmap here to
+	// FIXME: We should calculate a drawing offset for the pixmap here to
 	// adjust it.
     }