Set default tokens sent to 2 if fastbloom enabled

It makes sense to do this now that we have a default token log that's
actually able to accept tokens.

quinn-proto/src/config/mod.rs

@@ -506,7 +506,8 @@ impl ValidationTokenConfig {
     ///
     /// This refers only to tokens sent in NEW_TOKEN frames, in contrast to retry tokens.
     ///
-    /// Defaults to 0.
+    /// If the `fastbloom` feature is enabled (which it is by default), defaults to 2. Otherwise,
+    /// defaults to 0.
     pub fn sent(&mut self, value: u32) -> &mut Self {
         self.sent = value;
         self
@@ -522,7 +523,7 @@ impl Default for ValidationTokenConfig {
         Self {
             lifetime: Duration::from_secs(2 * 7 * 24 * 60 * 60),
             log,
-            sent: 0,
+            sent: if cfg!(feature = "fastbloom") { 2 } else { 0 },
         }
     }
 }