Add an example of how the host tag syntax looks (open-telemetry#27423)

It is not clear from the example how the tags should be written down.

**Description:** <Describe what has changed.>
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Co-authored-by: Yang Song <[email protected]>
Co-authored-by: Mackenzie <[email protected]>

exporter/datadogexporter/examples/collector.yaml

@@ -372,7 +372,7 @@ exporters:
       ##
       ## To attach tags to telemetry signals regardless of the host, use a processor instead.
       #
-      # tags: []
+      # tags: ["team:infra", "<TAG_KEY>:<TAG_VALUE>"]
 
     ## @param logs - custom object - optional
     ## Logs exporter specific configuration.