Removed outdated readme.txt (#12296)

uitest/src/main/webapp/VAADIN/readme.txt

@@ -1,15 +0,0 @@
-======================
-Themes and Widget Sets
-======================
-
-The WebContent/VAADIN directory contains Themes and Widgetsets.
-
-------
-Themes
-------
-
-Themes may be edited freely. They contain static images, CSS,
-and layouts for Vaadin applications.
-
-See http://dev.vaadin.com/wiki/DevDocs/StartingDevelopment for instructions for
-installing GWT and compiling widgetsets for Vaadin development.