Remove dev guide ie9 as it is no longer supported (#350)

FrankHossfeld · web-flow · commit 586370f17e8d · 2024-01-08T09:11:30.000-06:00
diff --git a/src/main/markdown/doc/latest/DevGuideIE9.md b/src/main/markdown/doc/latest/DevGuideIE9.md
@@ -1,6 +1,8 @@
 IE9
 ===
 
+**This document is deprecated: Starting with version 2.10.0, GWT no longer supports IE9!**
+
 ## Things to keep in mind<a id="Overview"></a>
 
 ### Modes
