Revert "woodpecker server env vars aren't replaced in image specs"

This reverts commit 0258d2d8a4.

.woodpecker/.build.yaml

@@ -12,7 +12,7 @@ when:
 
 steps:
   - name: build
-    image: gcr.io/kaniko-project/executor:v1.20.1-debug
+    image: gcr.io/kaniko-project/executor:$KANIKO_VER-debug
     environment:
       - container=kube
     commands:

renovate.json

@@ -4,10 +4,5 @@
     "config:recommended",
     ":preserveSemverRanges",
     "regexManagers:dockerfileVersions"
-  ],
-  "helm-values": {
-    "fileMatch": [
-      "^\\.woodpecker/\\.build\\.yaml$"
-    ]
-  }
+  ]
 }