Change default HTTP exporter port to 55681

[NathanielRN]

Which problem is this PR solving?

Fixes: #2330

Short description of the changes

• Changes default HTTP exporter port to be 55681 instead of 4317 because 4317 is reserved for gRPC in the specs
• 55681 is used by opentelemetry-collector so it should be a good choice

[codecov]

Codecov Report

Merging #2331 (4639c09) into main (6e82726) will not change coverage.
The diff coverage is n/a.

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##             main    #2331   +/-   ##
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  Coverage   92.77%   92.77%           
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  Files         145      145           
  Lines        5216     5216           
  Branches     1068     1068           
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  Hits         4839     4839           
  Misses        377      377           

[vmarchaud]

I believe you'll also need to change the default there:

• https://github.com/open-telemetry/opentelemetry-js/blob/main/packages/opentelemetry-exporter-collector-proto/src/CollectorMetricExporter.ts#L27