remove too_slow_to_test flag

this flag was added to deal with inefficiencies of Icehouse. this
patch removes flag as it's not used in post-Icehouse

Change-Id: Ib715e68dc61f3c3ea0a40fae0ea57028e36285bd
Depends-On: I842dfe04725b2482399c0e95b54403fb82001645

Author: chungg

lib/tempest

@@ -447,9 +447,6 @@ function configure_tempest {
     iniset $TEMPEST_CONFIG scenario large_ops_number ${TEMPEST_LARGE_OPS_NUMBER:-0}
 
     # Telemetry
-    # Ceilometer API optimization happened in Juno that allows to run more tests in tempest.
-    # Once Tempest retires support for icehouse this flag can be removed.
-    iniset $TEMPEST_CONFIG telemetry too_slow_to_test "False"
     iniset $TEMPEST_CONFIG telemetry-feature-enabled events "True"
 
     # Object Store