fix docker/build-push-action arguments

Author: haarg

.github/workflows/build-deployment-container.yml

@@ -31,7 +31,7 @@ jobs:
         uses: docker/build-push-action@v5
         with:
           push: true
-          build-arg:
+          build-args:
             - SLIM_BUILD=1
           tags: metacpan/metacpan-base:$GITHUB_SHA-slim
           platforms: linux/amd64,linux/arm64

.github/workflows/build-production-container.yml

@@ -30,7 +30,7 @@ jobs:
         uses: docker/build-push-action@v5
         with:
           push: true
-          build-arg:
+          build-args:
             - SLIM_BUILD=1
           tags: metacpan/metacpan-base:latest-slim
           platforms: linux/amd64,linux/arm64