[consensus] reduce leader timeout to 200ms (#21446)

## Description 

With round interval of 70-80ms, using 250ms for leader timeout seems a
bit excessive.

## Test plan 

PT

---

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

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that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] gRPC:
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:

consensus/config/src/parameters.rs

@@ -94,7 +94,7 @@ pub struct Parameters {
 
 impl Parameters {
     pub(crate) fn default_leader_timeout() -> Duration {
-        Duration::from_millis(250)
+        Duration::from_millis(200)
     }
 
     pub(crate) fn default_min_round_delay() -> Duration {

consensus/config/tests/snapshots/parameters_test__parameters.snap

@@ -4,7 +4,7 @@ expression: parameters
 ---
 leader_timeout:
   secs: 0
-  nanos: 250000000
+  nanos: 200000000
 min_round_delay:
   secs: 0
   nanos: 50000000