Fix build-args in workflows

(cherry picked from commit a4aa4201f02b613ab23fdd3fe45db2c129a2baca)

.github/workflows/docker_stable.yaml

@@ -36,7 +36,7 @@ jobs:
           push: true
           target: production
           build-args:
-            branch: stable
+            branch=stable
           tags: inventree/inventree:stable
       - name: Image Digest
         run: echo ${{ steps.docker_build.outputs.digest }}

.github/workflows/docker_tag.yaml

@@ -34,5 +34,5 @@ jobs:
           push: true
           target: production
           build-args:
-            tag: ${{ github.event.release.tag_name }}
+            tag=${{ github.event.release.tag_name }}
           tags: inventree/inventree:${{ github.event.release.tag_name }}