Update drone CI/CD

.drone.yml

@@ -3,8 +3,6 @@ name: default
 type: docker
 
 environment:
-  GRADLE_VERSION: 7.1
-  JDK_VERSION: 11
   CRE_VERSION: $DRONE_PULL_REQUEST
   CRE_ARTIFACT_NAME: ColorRecipesExplorer-backend-$CRE_VERSION
   CRE_REGISTRY_IMAGE: registry.fyloz.dev:5443/colorrecipesexplorer/backend
@@ -12,12 +10,12 @@ environment:
 
 steps:
   - name: test
-    image: gradle:$GRADLE_VERSION-jdk$JDK_VERSION
+    image: gradle:7.1-jdk11
     commands:
       - gradle test
 
   - name: build
-    image: gradle:$GRADLE_VERSION-jdk$JDK_VERSION
+    image: gradle:7.1-jdk11
     commands:
       - gradle bootJar -Pversion=$CRE_VERSION
       - mv build/libs/ColorRecipesExplorer-$CRE_VERSION.jar $CRE_ARTIFACT_NAME
@@ -29,7 +27,7 @@ steps:
     image: plugins/docker
     settings:
       build_args:
-        - JDK_VERSION=$JDK_VERSION
+        - JDK_VERSION=11
         - PORT=$CRE_PORT
         - ARTIFACT_NAME=$CRE_ARTIFACT_NAME
       repo: $CRE_REGISTRY_IMAGE