build.properties: remove JVM args that are no longer supported by modern Java VMs

Using these options will cause the build to report an error and fail

build.properties

diff --git a/build.properties b/build.properties
index be2b672..934cd8f 100644
--- a/build.properties
+++ b/build.properties
@@ -31,7 +31,7 @@
 flexdebug = true
 
 # JVM options for <compc> and <mxmlc> tasks
-jvm.args = ${local.d32} -Xms64m -Xmx1024m -XX:MaxPermSize=1024m -XX:+CMSClassUnloadingEnabled -ea -Dapple.awt.UIElement=true
+jvm.args = ${local.d32} -Xms64m -Xmx1024m -ea -Dapple.awt.UIElement=true
     # -d32/-d64 for 32-bit/64-bit code model (or don't specify for the default)
 	# -Xms64m: start out with a 64 MB heap
 	# -Xmx512m: allow the heap to grow to 512 MB