Only run Java 11 tests on merge

Author: OlivierBlanvillain

.drone.yml

@@ -48,6 +48,8 @@ pipeline:
     commands:
       - cp -R . /tmp/6/ && cd /tmp/6/
       - JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64/" ./project/scripts/sbt -java-home "/usr/lib/jvm/java-11-openjdk-amd64/" ";dotty-bootstrapped/compile ;dotty-bootstrapped/test; dotty-semanticdb/compile; dotty-semanticdb/test:compile;sjsSandbox/run;sjsSandbox/test"
+    when:
+      event: [ push, tag, deployment ]
 
   test_sbt:
     group: test