[TASK] Update composer manifest for 3.0.0-beta6
[TASK] Update composer manifest for 3.0.0-beta6

See https://jenkins.neos.io/job/Flow%20-%20Release/58/

Releases: 3.0
Original-Commit-Hash: 3e973946c1e0d613ada1cb0b1d4b5d5bde46d5e2

neos/fluid,neos/fluid