Use heat's default value for max_template_size

Instead of aligning value with tempest, make tempest use heat's default
value as that is what most people will be deploying with.

Change-Id: I77549f2b5e953ff712c50a2b372f6b04725d5eb0
diff --git a/lib/heat b/lib/heat
index 8acadb4..da4505e 100644
--- a/lib/heat
+++ b/lib/heat
@@ -118,9 +118,6 @@
     iniset $HEAT_CONF heat_api_cloudwatch bind_host $HEAT_API_CW_HOST
     iniset $HEAT_CONF heat_api_cloudwatch bind_port $HEAT_API_CW_PORT
 
-    # Set limits to match tempest defaults
-    iniset $HEAT_CONF DEFAULT max_template_size 10240
-
     # heat environment
     sudo mkdir -p $HEAT_ENV_DIR
     sudo chown $STACK_USER $HEAT_ENV_DIR