chore(deps): update docker/build-push-action action to v6.19.2

Author: renovate[bot]

.github/workflows/build-testflinger-testenv-container.yml

@@ -58,7 +58,7 @@ jobs:
           tags: ${{ matrix.version }}
 
       - name: Build and push backend Docker image
-        uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6.18.0
+        uses: docker/build-push-action@10e90e3645eae34f1e60eeb005ba3a3d33f178e8 # v6.19.2
         with:
           context: ./agent/extra/testflinger-testenv
           push: true

.github/workflows/server-charm-release.yml

@@ -66,7 +66,7 @@ jobs:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
 
       - name: Build and push backend Docker image
-        uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6.18.0
+        uses: docker/build-push-action@10e90e3645eae34f1e60eeb005ba3a3d33f178e8 # v6.19.2
         with:
           context: ./server
           build-contexts: |