Allow vendor-init-settable to persist.sys.zram_enabled

persist.sys.zram_enabled is set in vendor/build.prop in taimen and walleye,
which was added after the initial whitelist.
go/treble-sysprop-compatibility requires whitelisting such a property to
allow it to be overridden by vendor/{default|build}.prop.

Bug: 73905119
Test: succeeded building and test with taimen
Change-Id: I931182aa05eb90c14df6e2c7cc26913f3874fa18

public/property_contexts

@@ -118,6 +118,7 @@ vold.post_fs_data_done u:object_r:exported2_vold_prop:s0 exact int
 sys.retaildemo.enabled u:object_r:exported3_system_prop:s0 exact int
 
 # vendor-init-settable|vendor-init-actionable
+persist.sys.zram_enabled u:object_r:exported2_system_prop:s0 exact bool
 sys.usb.config u:object_r:exported_system_radio_prop:s0 exact string
 sys.usb.configfs u:object_r:exported_system_radio_prop:s0 exact int