Use proper path in service file

Using '/usr/bin/env' is now an antipattern.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I1e37bf97f16b74eab2e4d40892e042f03dd5023b
diff --git a/xyz.openbmc_project.Hwmon@.service b/xyz.openbmc_project.Hwmon@.service
index 29ab262..a400912 100644
--- a/xyz.openbmc_project.Hwmon@.service
+++ b/xyz.openbmc_project.Hwmon@.service
@@ -5,6 +5,6 @@
 
 [Service]
 Restart=on-failure
-ExecStart=/usr/bin/env phosphor-hwmon-readd -i ${HW_SENSOR_ID} -o %I
+ExecStart=/usr/bin/phosphor-hwmon-readd -i ${HW_SENSOR_ID} -o %I
 SyslogIdentifier=phosphor-hwmon-readd
 EnvironmentFile=/etc/default/obmc/hwmon/%I.conf