3ae72e7867ci: Disable Docker build summary generation (Hennadii Stepanov) Pull request description: The generated Docker build [summaries](https://github.com/bitcoin-core/secp256k1/actions/runs/21595861407) provide little practical value to the development workflow and clutter the CI output. This PR disables them. ACKs for top commit: real-or-random: utACK3ae72e7867Tree-SHA512: 0b28520765d5aa1c43ae7025c9be082742bc3784f743b4983947236bceb0255b2fa82cdf81d284470eeb83bda72b442019e051048319681bff09ac190d9b52f6