Allow graphics_config_writable_prop to be modified.

vendor_init needs to set graphics_config_writable_prop, moving it to
system_public_prop.

Bug: b/270994705
Test: atest CtsAngleIntegrationHostTestCases
Test: m && boot
Change-Id: I2f47c1048aad4565cb13d4289b9a018734d18c07
diff --git a/private/gpuservice.te b/private/gpuservice.te
index 08c3902..297a876 100644
--- a/private/gpuservice.te
+++ b/private/gpuservice.te
@@ -64,6 +64,8 @@
 # Needed for enabling write access to persist.graphics.egl from developer option switch UI, through gpuservice.
 set_prop(gpuservice, graphics_config_writable_prop)
 
+neverallow { domain -init -vendor_init -gpuservice } graphics_config_writable_prop:property_service set;
+
 # Needed for querying permission
 allow gpuservice permission_service:service_manager find;