Enable TIER1 outbound by default (#9349)

This PR sets the default value for the `tier1.enable_outbound` parameter in the network config to `true`.

We are comfortable changing the default now that TIER1 has been voluntarily enabled by many validators in mainnet and used without incident for more than 2 months. At the time of this PR, more than 40 mainnet validators have TIER1 outbound enabled. 

The `enable_outbound` parameter will continue to exist, allowing for validators to opt out of the TIER1 network if desired.

chain/network/src/config_json.rs

@@ -197,10 +197,8 @@ pub struct Config {
 fn default_tier1_enable_inbound() -> bool {
     true
 }
-/// This default will be changed over the next releases.
-/// It allows us to gradually roll out the TIER1 feature.
 fn default_tier1_enable_outbound() -> bool {
-    false
+    true
 }
 
 fn default_tier1_connect_interval() -> Duration {