Update .gitlab-ci.yml

.gitlab-ci.yml

 image: maven:3.8.3-openjdk-17
 
 variables:
-  MAVEN_OPTS: "-DskipUiTests=true"
   MAVEN_CLI_OPTS: "--batch-mode -P headless"
 
 stages:
@@ -16,10 +15,10 @@ cache:
 test:
   stage: test
   script:
-    - mvn clean test -f todolist/pom.xml
+    - mvn clean test -f todolist/pom.xml "-DskipUiTests=true"
 
 build:
   stage: build
   when: manual
   script:
-    - mvn clean install -f todolist/pom.xml
+    - mvn clean install -f todolist/pom.xml "-DskipUiTests=true"