remove native dockerfile as it's not in use currently

src/main/docker/Dockerfile.native

-####
-# This Dockerfile is used in order to build a container that runs the Quarkus application in native (no JVM) mode
-#
-# Before building the docker image run:
-#
-# mvn package -Pnative -Dquarkus.native.container-build=true
-#
-# Then, build the image with:
-#
-# docker build -f src/main/docker/Dockerfile.native -t quarkus/gitlab.cla .
-#
-# Then run the container using:
-#
-# docker run -i --rm -p 8080:8080 quarkus/gitlab.cla
-#
-###
-FROM registry.access.redhat.com/ubi8/ubi-minimal
-WORKDIR /work/
-COPY target/*-runner /work/application
-RUN chmod 775 /work
-EXPOSE 8080
-CMD ["./application", "-Dquarkus.http.host=0.0.0.0"]
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