Fix(Develop): Change unit from 's' to 'second' in telemetry docs (#15662)

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The snippet is using the incorrect unit, I altered it so the JavaScript
matches the correct unit.
<img width="1052" height="421" alt="image"
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Author: lucas-zimerman

develop-docs/sdk/telemetry/scopes.mdx

@@ -72,7 +72,7 @@ Sentry.getGlobalScope().setAttributes({
   "app.feature_flag.enabled": true,
   "app.session_duration": {
     value: 3600,
-    unit: "s"
+    unit: "second"
   }
 });
 ```