Fix incorrect `elasticapm` link

[alexandra5000]

Based on this request:

Hi team,
I noted that in this documentation page https://www.elastic.co/docs/reference/edot-collector/config/default-config-standalone#application-and-traces-collection-pipeline the elasticapm connector and processor links points to the elasticapmprocessor. Can we fix the links?

[theletterf]

@alexandra5000 Now that we have processor docs here, we can link the processor to https://www.elastic.co/docs/reference/edot-collector/components/elasticapmprocessor