Fix bounds in computeLoEMaxExtra

As it was before, the code would in fact never return `Just 0`, only
`Nothing` or `Just x` with `x > 0`.

ouroboros-consensus/src/ouroboros-consensus/Ouroboros/Consensus/Storage/ChainDB/Impl/ChainSel.hs

@@ -811,14 +811,14 @@ chainSelectionForBlock cdb@CDB{..} blockCache hdr punish = electric $ do
     computeLoEMaxExtra (LoEEnabled loeFrag) newBlockFrag =
         -- Both fragments are on the same chain
         if loeSuffixLength == 0 || rollback == 0 then
-          if rollback < k + loeSuffixLength
+          if rollback <= k + loeSuffixLength
             then Just $ LoEEnabled $ k + loeSuffixLength - rollback
             else Nothing
         else
           -- REVIEW: Since we filter out candidates that fork off the LoE later,
           -- it does not really matter what we return here and we could just
           -- return @Nothing@ or merge it in the previous case.
-          if rollback < k
+          if rollback <= k
             then Just $ LoEEnabled $ k - rollback
             else Nothing
       where