chore(deps): update dependency chainguard-dev/melange to v0.15.7

tools/melange/manifest.yaml

 # yaml-language-server: $schema=https://tools.uniget.dev/schema.yaml
 name: melange
-version: "0.15.6"
+version: "0.15.7"
 check: ${binary} version 2>&1 | grep ^GitVersion | tr -s ' ' | cut -d' ' -f2 | tr -d v
 build_dependencies:
 - go