Changed license of .protoc definition to Apache-2.0

[cmaglie]

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• Tests for the changes have been added (for bug fixes / features)
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What kind of change does this PR introduce?

Change the license of .protoc definitions to a more permissive Apache-2.0.

What is the current behavior?

What is the new behavior?

Does this PR introduce a breaking change, and is titled accordingly?

Other information

Fix #1957

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.23%. Comparing base (850f22a) to head (d2cc50a).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2653   +/-   ##
=======================================
  Coverage   70.23%   70.23%           
=======================================
  Files         222      222           
  Lines       21347    21347           
=======================================
  Hits        14993    14993           
  Misses       5175     5175           
  Partials     1179     1179           

Flag	Coverage Δ
unit	70.23% <ø> (ø)

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