fix: Fix javadoc generation on Java11

[vam-google]

Without this fix gradle fails witht he following error for publishing taks (like ./gradlew clean publishMavenJavaPublicationToMavenLocal) when built on Java 11 (it used to work normally on Java 8)

javadoc: error - The code being documented uses modules but the packages defined in https://docs.oracle.com/javase/7/docs/api/ are in the unnamed module

[codecov]

Codecov Report

Merging #1145 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #1145   +/-   ##
=========================================
  Coverage     78.65%   78.65%           
  Complexity     1170     1170           
=========================================
  Files           204      204           
  Lines          5195     5195           
  Branches        417      417           
=========================================
  Hits           4086     4086           
  Misses          935      935           
  Partials        174      174           

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