[chore][extension/remotetap] fix component name in README (#32581)

`remoteobserver` => `remotetap`

The type name `remoteObserverExtension` should also be changed for
consistency @atoulme.

extension/remotetapextension/README.md

@@ -25,7 +25,7 @@ Example:
 ```yaml
 
 extensions:
-  remoteobserver:
+  remotetap:
 ```
 
 The full list of settings exposed for this exporter are documented [here](./config.go).