Revert "chore(java11): compile with Java 11 (but using -source 8 -target 8)"

[plumpy]

Reverts #1108

[spinnakerbot]

The following commits need their title changed:

• dab1dec: Revert "chore(java11): compile with Java 11 (but using -source 8 -target 8) (chore(java11): compile with Java 11 (but using -source 8 -target 8) #1108)"

Please format your commit title into the form:

<type>(<scope>): <subject>, e.g. fix(kubernetes): address NPE in status check

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