Make 'prop_runSelection_UTxO_muchMoreThanEnough' blind about 'UTxOIndex'

  Failures generate unreadable output which are pointless. For this test, it'll be better to rely on counterexample built for
  analyzing failures.

lib/core/test/unit/Cardano/Wallet/Primitive/CoinSelection/MA/RoundRobinSpec.hs

@@ -81,6 +81,7 @@ import Test.Hspec.Core.QuickCheck
     ( modifyMaxSuccess )
 import Test.QuickCheck
     ( Arbitrary (..)
+    , Blind (..)
     , Gen
     , Positive (..)
     , Property
@@ -289,8 +290,8 @@ prop_runSelection_UTxO_moreThanEnough (Small index) = monadicIO $ do
         cutAssetSetSizeInHalf balanceAvailable
 
 prop_runSelection_UTxO_muchMoreThanEnough
-    :: Large UTxOIndex -> Property
-prop_runSelection_UTxO_muchMoreThanEnough (Large index) =
+    :: Blind (Large UTxOIndex) -> Property
+prop_runSelection_UTxO_muchMoreThanEnough (Blind (Large index)) =
     -- Generation of large UTxO sets takes longer, so limit the number of runs:
     withMaxSuccess 100 $
     checkCoverage $