docs(exporter/newrelicexporter/README.md): Update the new relic exporter documents

[Shihao-Zhong]

Description:

Update the new relic exporter's config example.

Link to tracking Issue:
There is no issue for that yet.

Testing:
There is no code changes.

Documentation:
There have a release (0.25.0) had updated the new relic exporter's configuration format. But the new document's config sample is not correct(#3091). The existing documents shows.

exporters:
  newrelic:
    apikey: super-secret-api-key
    timeout: 30s

  # host_override is set to send data to New Relic's EU data centers.
  traces:
    host_override: trace-api.eu.newrelic.com
    timeout: 20s
  metrics:
    host_override: metric-api.eu.newrelic.com
  logs:
    host_override: log-api.eu.newrelic.com

But the correct format should be

exporters:
  newrelic:
    apikey: super-secret-api-key
    timeout: 30s

    # host_override is set to send data to New Relic's EU data centers.
    traces:
      host_override: trace-api.eu.newrelic.com
      timeout: 20s
    metrics:
      host_override: metric-api.eu.newrelic.com
    logs:
      host_override: log-api.eu.newrelic.com

[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Shihao-Zhong (cbd4aad, 0249aa0)

[codecov]

Codecov Report

Merging #3194 (bbc2ac5) into main (be47f6f) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #3194   +/-   ##
=======================================
  Coverage   91.92%   91.92%           
=======================================
  Files         493      493           
  Lines       23946    23946           
=======================================
  Hits        22012    22012           
  Misses       1428     1428           
  Partials      506      506           

Flag	Coverage Δ
integration	63.35% <ø> (-0.06%)	⬇️
unit	90.94% <ø> (ø)

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[bogdandrutu]

Please sign the CLA

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Thanks for your contribution @Shihao-Zhong ! ❤️