Update .gitlab-ci.yml

.gitlab-ci.yml

-javadoc:jdk8:
-  stage: test
-  script:
-    - 'mvn $MAVEN_CLI_OPTS javadoc:aggregate-jar'
+image: java:latest
+
+stages:
+  - execute
+
+build:
+  stage: build
+  script: javadoc complexityparser/src/main/java/Main.java
+