Remove SegWit references from RPC help

(that other unwanted soft fork)

Tested as follows in debug console (prepend bitcoin-cli on command line):

1. help getblocktemplate
2. help getrawtransaction
3. help decoderawtransaction

Expected outputs:

For 1: description of hash field should be (string) hash encoded in little-endian hexadecimal

For 2 & 3 : description of hash field should be (string) The transaction hash