deadlock-free transactions in the release notes

[Dmitriy Setrakyan]

Igniters,

The release notes for 1.5-b1 [1] are missing the Deadlock-free
transactions. Should we add them?

[1]
https://github.com/apache/ignite/blob/ignite-1.5.0-b1-rc1/RELEASE_NOTES.txt

D.