Fix typo in application.conf comment (#5576)

Correct 'kamon.prometehus' to 'kamon.prometheus' in the HOCON comment.
The actual config block name is 'prometheus'.

Signed-off-by: Shion Ichikawa <shion1305@gmail.com>

Author: Shion1305

common/scala/src/main/resources/application.conf

@@ -321,7 +321,7 @@ whisk {
                 # Sets the maximum number of retries in the case where the request fails
                 # because the service has applied rate limiting on the client.
 
-                # If this value is changed then adjust the buckets under `kamon.prometehus`
+                # If this value is changed then adjust the buckets under `kamon.prometheus`
                 max-retry-attempts-on-throttled-requests = 9
 
                 # Sets the maximum retry time