fix(prover): Fixing shutdown time for circuit-prover (matter-labs#3768)

## What ❔
Fixed shutdown time for circuit-prover. Metrics didn't allow
circuit-prover to exit properly on SIGTERM
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## Why ❔
Circuit-prover was waiting for GRACEFUL_SHUTDOWN_TIME timeout regardless
whether it had jobs or not. Metrics didn't exit properly.
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## Is this a breaking change?
- [ ] Yes
- [ ] No

## Operational changes
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## Checklist

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- [ ] PR title corresponds to the body of PR (we generate changelog
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- [ ] Tests for the changes have been added / updated.
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lint`.

Author: AlexOnTheStorm

prover/crates/bin/circuit_prover/src/main.rs

@@ -141,14 +141,11 @@ async fn main() -> anyhow::Result<()> {
         }
     }
     let shutdown_time = Instant::now();
-    tasks.complete(GRACEFUL_SHUTDOWN_DURATION).await;
-    PROVER_BINARY_METRICS
-        .shutdown_time
-        .observe(shutdown_time.elapsed());
-    PROVER_BINARY_METRICS.run_time.observe(start_time.elapsed());
     metrics_stop_sender
         .send(true)
         .context("failed to stop metrics")?;
+    tasks.complete(GRACEFUL_SHUTDOWN_DURATION).await;
+    tracing::info!("Tasks completed in {:?}.", shutdown_time.elapsed());
     Ok(())
 }
 /// Loads configs necessary for proving.