[chore] Update README.md to correctly reflect OTLP Protocol version

[cijothomas]

https://github.com/open-telemetry/opentelemetry-collector/blob/main/Makefile#L174 shows v1.4.0, so the readme got stale?

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.62%. Comparing base (4cf491b) to head (c1e15c2). Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #11949   +/-   ##
=======================================
  Coverage   91.62%   91.62%           
=======================================
  Files         447      447           
  Lines       23729    23729           
=======================================
  Hits        21741    21741           
  Misses       1613     1613           
  Partials      375      375           

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[cijothomas]

One of the CI "contrib-tests / contrib-tests-matrix (exporter-1) (pull_request) Failing after 40s " is failing, probably unrelated to this change. Also wondering if the CI can be taught to not run entire suite of CI for changes that only touch .md files?