multi: Remove no longer relevant blake256 pad code.

[davecgh]

This removes the blake256 padding code since it no longer applies.

[jholdstock]

One more comment to update, otherwise looks good.

dcrpool/pool/hub.go

Lines 46 to 56 in 73a5cd5

	// getworkDataLen is the length of the data field of the getwork RPC.
	// It consists of the serialized block header plus the internal blake256
	// padding. The internal blake256 padding consists of a single 1 bit
	// followed by zeros and a final 1 bit in order to pad the message out
	// to 56 bytes followed by length of the message in bits encoded as a
	// big-endian uint64 (8 bytes). Thus, the resulting length is a
	// multiple of the blake256 block size (64 bytes). Given the padding
	// requires at least a 1 bit and 64 bits for the padding, the following
	// converts the block header length and hash block size to bits in order
	// to ensure the correct number of hash blocks are calculated and then
	// multiplies the result by the block hash block size in bytes.

[davecgh]

I was planning to update that in the separate blake3 commit, because it has to change for that.