Merge bitcoin/bitcoin#30819: doc: fix assumeutxo design doc link

e5f7272 doc: fix assumeutxo design doc link (marcofleon)

Pull request description:

  A correction to a link as I was exploring Assumeutxo stuff.

ACKs for top commit:
  fjahr:
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  tdb3:
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  MarnixCroes:
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Tree-SHA512: b7380d884a196b89eed32bc14af8ca11191c9f2bcb1c5c163bb627fd87a6231dbd86da6e659baddb8c652961b5e44f80509606fee9ae38a53e90ebb05d082404

Author: fanquake

doc/assumeutxo.md

@@ -3,7 +3,7 @@
 Assumeutxo is a feature that allows fast bootstrapping of a validating bitcoind
 instance.
 
-For notes on the design of Assumeutxo, please refer to [the design doc](/doc/assumeutxo.md).
+For notes on the design of Assumeutxo, please refer to [the design doc](/doc/design/assumeutxo.md).
 
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