Doc improvement - better example(s) of yml config stanzas to environment variables

[jtduffy]

https://docs.newrelic.com/docs/apm/agents/java-agent/configuration/java-agent-configuration-config-file/#Environment_Variables

Add an example of a complicated yml config --> environment variable:

common:
  class_transformer:
    com.newrelic.instrumentation.kafka-clients-spans-0.11.0.0:
      enabled: true

Environment variable:
NEW_RELIC_CLASS_TRANSFORMER_COM_NEWRELIC_INSTRUMENTATION_KAFKA_CLIENTS_SPANS_0_11_0_0_ENABLED

There is also an outdated section that states that For agent versions 4.10.0 or higher the following environment variables are available: and then lists 5 variables. This is incorrect since all config options are available as environment variables

[workato-integration]

https://new-relic.atlassian.net/browse/NR-150441