Remove BIP9 and BIP145 references from getblocktemplate RPC help

The RPC help for getblocktemplate refers to four BIPs (22/23/9/145), two of which are problematic:

1. It refers to the BIP9 specification, despite none of the getblocktemplate section of BIP9 currently being implemented (this caused the IFP voting problems in ABC 0.21.0).
2. It refers to the BIP145 specification, but the only visible remnant of this SegWit specification is that we have a txid field mirroring the hash field - referencing this specification thus adds more confusion than clarity.

This commit removes specification references to these two BIPs.

Tested as follows:

1. Review the diff of this MR.
2. In RPC console, help getblocktemplate.
3. Verify the changes.