[MTT-11838] Fix: upgrade unity transport to 2.5.1 and update banner in README.md#906

Elfi0Kuhndorf merged 3 commits intodevelopUnity-Technologies/com.unity.multiplayer.samples.coop:developfrom

fix-upgradeTransport_and_fix_bannerUnity-Technologies/com.unity.multiplayer.samples.coop:fix-upgradeTransport_and_fix_bannerCopy head branch name to clipboard