fix: sequencer negative histogram recodings (#10490)

Fix for these two otel warnings
```
negative value provided to histogram aztec.sequencer.state_transition_buffer.duration:

INT value type cannot accept a floating-point value for aztec.sequencer.state_transition_buffer.duration, ignoring the fractional digits.
```

Author: alexghr

yarn-project/sequencer-client/src/sequencer/sequencer.ts

@@ -385,14 +385,16 @@ export class Sequencer {
     }
 
     const bufferSeconds = this.timeTable[proposedState] - secondsIntoSlot;
-    this.metrics.recordStateTransitionBufferMs(bufferSeconds * 1000, proposedState);
 
     if (bufferSeconds < 0) {
       this.log.warn(
         `Too far into slot to transition to ${proposedState}. max allowed: ${this.timeTable[proposedState]}s, time into slot: ${secondsIntoSlot}s`,
       );
       return false;
     }
+
+    this.metrics.recordStateTransitionBufferMs(Math.floor(bufferSeconds * 1000), proposedState);
+
     this.log.debug(
       `Enough time to transition to ${proposedState}, max allowed: ${this.timeTable[proposedState]}s, time into slot: ${secondsIntoSlot}s`,
     );