Revert P2TR example from "BIP48: Add P2SH-P2WSH and P2TR mainnet examples"

This partially reverts commit 9c22bcef63.

bip-0048.mediawiki

@@ -192,13 +192,6 @@ Public derivation is used at this level.
 |second
 |m / 48' / 0' / 1' / 2' / 0 / 1
 |-
-|mainnet
-|first
-|p2tr
-|external
-|first
-|m / 48' / 0' / 0' / 3' / 0 / 0
-|-
 |testnet
 |first
 |p2sh-p2wsh