Remove Chrome Frame support from X-UA-Compatible (#9270)

Remove Chrome Frame specific part of X-UA-Compatible but keep the
meta tag to override compatibility mode settings where applicable.

server/src/main/java/com/vaadin/server/BootstrapHandler.java

@@ -516,11 +516,8 @@ public abstract class BootstrapHandler extends SynchronizedRequestHandler {
         head.appendElement("meta").attr("http-equiv", "Content-Type").attr(
                 "content", ApplicationConstants.CONTENT_TYPE_TEXT_HTML_UTF_8);
 
-        /*
-         * Enable Chrome Frame in all versions of IE if installed.
-         */
-        head.appendElement("meta").attr("http-equiv", "X-UA-Compatible")
-                .attr("content", "IE=11;chrome=1");
+        // Force IE 11 to use IE 11 mode.
+        head.appendElement("meta").attr("http-equiv", "X-UA-Compatible").attr("content", "IE=11");
 
         Class<? extends UI> uiClass = context.getUIClass();