1cdb9bb51f minor p2p_sendheaders fix of height in coinbase (Gregory Sanders)
Pull request description:
> \# Now announce a header that forks the last two blocks
Doesn't effect any behavior since BIP34 isn't active in regtest for many blocks.
Tree-SHA512: 3f214b956a94250bb640f63b6ff707930e1d4cb8df1bbf0fef4012d89a94bafbde0d7b42bbe7113ec33810169281c22c6e389445921d99decb74aa56e87a0f27
Backport of Core PR14543