Fix mistake in anchor outputs amounts

The "legacy" anchor outputs are always taken from the funder's main
output. Thanks @carlaKC for spotting this!

Author: t-bast

02-peer-protocol.md

@@ -2608,6 +2608,9 @@ A sending node:
         - MAY fail the channel
 
 A receiving node:
+  - if `zero_fee_commitments` is used:
+    - MUST ignore the message.
+    - SHOULD send a `warning` and disconnect.
   - if the `update_fee` is too low for timely processing, OR is unreasonably large:
     - MUST send a `warning` and close the connection, or send an
       `error` and fail the channel.

03-transactions.md

@@ -316,8 +316,8 @@ Before the commitment transaction outputs are determined:
   - the base fee MUST be subtracted from the `to_local` or `to_remote` output,
     as specified in [Fee Calculation](#fee-calculation).
   - if `option_anchors` applies:
-    - the `to_local_anchor` output value MUST be subtracted from the `to_local` output.
-    - the `to_remote_anchor` output value MUST be subtracted from the `to_remote` output.
+    - the `to_local_anchor` output value MUST be subtracted from the funder's output.
+    - the `to_remote_anchor` output value MUST be subtracted from the funder's output.
 
 The commitment transaction:
   - if the amount of the commitment transaction `to_local` output would be