Remove branch from `rightIndex`

packages/contracts-bedrock/.gas-snapshot

@@ -230,7 +230,7 @@ LegacyERC20ETH_Test:test_mint_doesNotExist_reverts() (gas: 10627)
 LegacyERC20ETH_Test:test_transferFrom_doesNotExist_reverts() (gas: 12957)
 LegacyERC20ETH_Test:test_transfer_doesNotExist_reverts() (gas: 10755)
 LegacyMessagePasser_Test:test_passMessageToL1_succeeds() (gas: 34524)
-LibPosition_Test:test_pos_correctness() (gas: 39343)
+LibPosition_Test:test_pos_correctness() (gas: 38668)
 MerkleTrie_get_Test:test_get_corruptedProof_reverts() (gas: 5736)
 MerkleTrie_get_Test:test_get_extraProofElements_reverts() (gas: 58975)
 MerkleTrie_get_Test:test_get_invalidDataRemainder_reverts() (gas: 35852)

packages/contracts-bedrock/contracts/dispute/lib/LibPosition.sol

@@ -114,14 +114,8 @@ library LibPosition {
     ) internal pure returns (Position rightIndex_) {
         uint256 msb = depth(_position);
         assembly {
-            switch eq(msb, _maxDepth)
-            case true {
-                rightIndex_ := _position
-            }
-            default {
-                let remaining := sub(_maxDepth, msb)
-                rightIndex_ := or(shl(remaining, _position), sub(shl(remaining, 1), 1))
-            }
+            let remaining := sub(_maxDepth, msb)
+            rightIndex_ := or(shl(remaining, _position), sub(shl(remaining, 1), 1))
         }
     }