tiproxy: fix image link in tiproxy-load-balance.md#20530

ti-chi-bot[bot] merged 1 commit intopingcap:release-8.5pingcap/docs-cn:release-8.5from

hfxsd:fix-image-link-for-8.5hfxsd/docs-cn:fix-image-link-for-8.5Copy head branch name to clipboard