[BIP 22 - getblocktemplate](https://github.com/bitcoin/bips/blob/master/bip-0022.mediawiki#Transactions%20Object%20Format) specifies an optional flag, `required` if the transaction must be in the block.

Luke's implementation #936 did not include this flag, and it was later added to the help description in #3246 (more than a year later) but the field was still never actually implemented. As far as I can tell, bitcoin core would have never actually included this in a `getblocktemplate` call, so it seems logical to remove it from the help description.

If I am missing something or this is considered harmless - I can close the PR.