chore(deps): pin ghcr.io/regclient/regctl docker tag to 0438daa

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Dockerfile

@@ -10,7 +10,7 @@ COPY ./ ./
 
 RUN CGO_ENABLED=0 go build -o /go/bin/composevalidate -trimpath -ldflags="-s -w" .
 
-FROM ghcr.io/regclient/regctl:alpine
+FROM ghcr.io/regclient/regctl:alpine@sha256:0438daa1d058a178920ea105af06dfc4308cb693b889754409c014923d06535a
 
 COPY --from=build /go/bin/composevalidate /usr/local/bin/