ref(metrics): Promote metrics capture API

Remove the remaining experimental annotation from SentryClient.captureMetric. The interface and high-level metrics API are already stable, while buffering and accumulation can continue evolving internally.

Refs #6408
Refs #6150
Refs #6151
Co-Authored-By: Claude <noreply@anthropic.com>

Author: adinauer

sentry/src/main/java/io/sentry/SentryClient.java

@@ -1350,7 +1350,6 @@ public void captureBatchedLogEvents(final @NotNull SentryLogEvents logEvents) {
     }
   }
 
-  @ApiStatus.Experimental
   @Override
   public void captureMetric(
       @Nullable SentryMetricsEvent metricsEvent,