Follow-up of JDK-8264139, but for the iOS sources in the javafx.web module.

Currently the warnings are considered as errors (-Werror is specified), and compilation fails:

> Task :web:compileJava FAILED
.../modules/javafx.web/src/ios/java/javafx/scene/web/HTMLEditorSkin.java:826: warning: [removal] AccessController in java.security has been deprecated and marked for removal
        Image icon = AccessController.doPrivileged(new PrivilegedAction<Image>() {
                     ^
error: warnings found and -Werror specified
...
1 error
9 warnings
...

The current workaround to avoid the error is using -PdisableJavacWerror=false.