Fix sysctl read sandbox violation in the GPU process

https://bugs.webkit.org/show_bug.cgi?id=274528
rdar://122952474

Reviewed by Chris Dumez.

Fix sysctl read sandbox violation in the GPU process on iOS by allowing reading a sysctl name
which has been confirmed to be in use.

* Source/WebKit/Resources/SandboxProfiles/ios/com.apple.WebKit.GPU.sb.in:

Canonical link: https://commits.webkit.org/279137@main

Source/WebKit/Resources/SandboxProfiles/ios/com.apple.WebKit.GPU.sb.in

@@ -577,6 +577,7 @@
         "kern.secure_kernel"
         "kern.osversion"
         "kern.willshutdown" ;; <rdar://122511261>
+        "machdep.ptrauth_enabled"
         "vm.footprint_suspend"
         "vm.malloc_ranges")) ;; <rdar://problem/105161083>