Revert "Add environement for flutter image"

This reverts commit 1442b1f6

.drone.yml

@@ -3,9 +3,6 @@ kind: pipeline
 name: build
 type: docker
 
-environment:
-  FLUTTER_IMAGE: jonasfranz/flutter:2.10.1
-
 workspace:
   path: "/app"
 
@@ -20,14 +17,14 @@ clone:
 steps:
   - name: build
     pull: always
-    image: ${FLUTTER_IMAGE}
+    image: jonasfranz/flutter:2.10.1
     commands:
       - flutter packages get
       - flutter build apk
 
   - name: lint
     pull: always
-    image: ${FLUTTER_IMAGE}
+    image: jonasfranz/flutter:2.10.1
     depends_on:
       - build
     commands:
@@ -36,7 +33,7 @@ steps:
 
   - name: test
     pull: always
-    image: ${FLUTTER_IMAGE}
+    image: jonasfranz/flutter:2.10.1
     depends_on:
       - build
     commands:
@@ -47,9 +44,6 @@ kind: pipeline
 name: metrics
 type: docker
 
-environment:
-  FLUTTER_IMAGE: jonasfranz/flutter:2.10.1
-
 depends_on:
   - build
 
@@ -63,7 +57,7 @@ platform:
 steps:
   - name: generate_metrics
     pull: always
-    image: ${FLUTTER_IMAGE}
+    image: jonasfranz/flutter:2.10.1
     commands:
       - flutter pub run dart_code_metrics:metrics analyze lib -r html
   - name: convert_to_latex