Revert inadvertently-changed maven compiler plugin version

[sliver007]

The maven compiler plugin version was incorrectly changed in a previous commit. This reverts that change.

• Github Issue:
• I've read the contribution guidelines
• Code compiles without errors
• Tests are created / updated
• Documentation is created / updated

By creating this PR you acknowledge that your contribution will be licensed under Apache 2.0

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 19.92%. Comparing base (11b055c) to head (441c346).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #597   +/-   ##
=========================================
  Coverage     19.92%   19.92%           
  Complexity     1687     1687           
=========================================
  Files           312      312           
  Lines         27689    27689           
  Branches       4376     4376           
=========================================
  Hits           5517     5517           
  Misses        21242    21242           
  Partials        930      930           

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