Remove unnecessary files

.gitlab-ci.yml

-image: maven:latest
-
-stages:
-    - compile
-    - test
-    - deploy
-
-compile:
-    stage: compile
-    script:
-      - mvn compile
-
-test:
-    stage: test
-    script:
-      - mvn test
-
-deploy:
-    stage: deploy
-    image: ruby:latest
-    script:
-      - gem install dpl 
-      - dpl --provider=heroku --app=jlp19-simplewebapp --api-key=$Heroku_API_Key

Dockerfile

-FROM maven:3.6.0-jdk-11-slim
-
-# Install necessary dependencies
-RUN apt-get -y update
-RUN apt-get -y install texlive-latex-base texlive-fonts-recommended texlive-latex-extra pandoc
-
-# Copy source files
-COPY src /src
-COPY pom.xml /
-
-# Start application
-RUN mvn package
-EXPOSE 8080
-CMD ["sh", "target/bin/simplewebapp"]

heroku.yml

-build:
-  docker:
-    web: Dockerfile
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