Fix mistake in bip-0079

As pointed out by Adam Gibson on the bitcoin-dev mailing list.

Author: RHavar

bip-0079.mediawiki

@@ -49,9 +49,9 @@ This is done via an HTTP POST request, sent to a "bustapay url"
 
 The receiver validates the transaction, and pays himself. The receiver then adds one or more of his own inputs (known as the ''contributed inputs'') and (optionally) increases the output that pays himself (generally by the sum of the ''contributed inputs''). Doing so creates a ''partial transaction'', which the receiver returns to the sender. It is called such as it requires the sender to resign his own inputs.
 
-====Step 4. Receiver validates, re-signs, and propagates on the bitcoin network====
+====Step 4. Sender validates, re-signs, and propagates on the bitcoin network====
 
-The receiver MUST validate the ''partial transaction'' was changed correctly and non-maliciously (to allow using potentially untrusted communication channels), resign its original inputs and propagates the final transaction over the bitcoin network.
+The sender MUST validate the ''partial transaction'' was changed correctly and non-maliciously (to allow using potentially untrusted communication channels), resign its original inputs and propagates the final transaction over the bitcoin network.
 
 ====Step 5. Receiver observes the finalized transaction on the bitcoin network====
 
@@ -79,7 +79,7 @@ It is strongly preferable that the receiver makes an effort to pick a contribute
 
 === Output Adjustment ===
 
-After adding inputs to the transaction, the receiver generally will want to adjust the output that pays himself by increasing it by the sum of the contributed input amounts (minus any fees he wants to contribute). However the only strict requirement is that the receiver *must never* add or remove inputs, and *must not* ever decrease any output amount.
+After adding inputs to the transaction, the receiver generally will want to adjust the output that pays himself by increasing it by the sum of the contributed input amounts (minus any fees he wants to contribute). However the only strict requirement is that the receiver *must never* remove inputs, and *must not* ever decrease any output amount.
 
 === Returning the partial transaction ===