Try to fix thermal-engine dac_override denial.

We saw a similar denial on Marlin where thermal_engine was trying to
access /dev/diag.  This ports that fix to Wahoo to try to fix its
denial.

Bug: 78019417
Test: Build policy.
Change-Id: I3702e705ea4f99a58f4b96008d236d33ecd8045c
diff --git a/init.hardware.rc b/init.hardware.rc
index 630e015..45c4c14 100644
--- a/init.hardware.rc
+++ b/init.hardware.rc
@@ -506,7 +506,7 @@
 service thermal-engine /vendor/bin/thermal-engine -c ${sys.qcom.thermalcfg:-/vendor/etc/thermal-engine.conf}
    class main
    user root
-   group root system
+   group root system diag
    socket thermal-send-client stream 0666 system system
    socket thermal-recv-client stream 0660 system system
    socket thermal-recv-passive-client stream 0666 system system