Remove conflicting -U option for apk in Dockerfile (#5578)

The `--no-cache` option updates the index and avoids temporary files, making `-U` unnecessary, consistent with the subsequent `apk add`.

Dockerfile

@@ -9,7 +9,7 @@ RUN go build ./cmd/nuclei
 
 # Release
 FROM alpine:3.18.6
-RUN apk -U upgrade --no-cache \
+RUN apk upgrade --no-cache \
     && apk add --no-cache bind-tools chromium ca-certificates
 COPY --from=build-env /app/nuclei /usr/local/bin/