fix(ci): set build_target to 'application' to reduce Docker image size (#7913)

Should be done after #7909 is
merged

Author: aldy505

.github/workflows/image.yml

@@ -31,6 +31,7 @@ jobs:
         image_name: 'snuba'
         platforms: linux/${{ matrix.platform }}
         dockerfile_path: 'Dockerfile'
+        build_target: 'application'
         tag_suffix: -${{ matrix.platform }}
         ghcr: true
         tag_nightly: false