Added two warnings to Operations Monitoring documentation (#33385)

Warning 1: Do not use whitespaces in the Operation's name.
Warning 2: The operationKey value must be the same.

Author: arti-arutiunov

content/en/real_user_monitoring/operations_monitoring.md

@@ -91,6 +91,8 @@ RUMMonitor.shared().startFeatureOperation(
 {{% /tab %}}
 {{< /tabs >}}
 
+<div class="alert alert-warning">The Operation's name cannot contain any whitespaces.</div>
+
 ### Stop an operation with success
 
 Every started operation must have a stop. Use `succeedFeatureOperation` to stop an operation with a successful outcome.
@@ -140,6 +142,8 @@ RUMMonitor.shared().succeedFeatureOperation(
 {{% /tab %}}
 {{< /tabs >}}
 
+<div class="alert alert-warning">The <code>operationKey</code> must be the same in the start and end Operation event.</div>
+
 ### Stop an operation with failure
 
 Every started operation must have a stop. Use `failFeatureOperation` to stop an operation with a failure outcome.