fix: [L04] updatedRelayerFeePct can be lower than expected

.eslintignore

@@ -4,3 +4,5 @@ cache
 coverage*
 gasReporterOutput.json
 typechain
+artifacts-zk
+cache-zk

.npmignore

@@ -1,2 +1,3 @@
 hardhat.config.ts
 cache
+cache-zk

.prettierignore

@@ -5,3 +5,5 @@ coverage*
 gasReporterOutput.json
 typechain
 dist
+artifacts-zk
+cache-zk

contracts/SpokePool.sol

@@ -460,7 +460,7 @@ abstract contract SpokePool is
         bytes memory updatedMessage,
         bytes memory depositorSignature
     ) public override nonReentrant {
-        require(updatedRelayerFeePct < 0.5e18, "invalid relayer fee");
+        require(SignedMath.abs(updatedRelayerFeePct) < 0.5e18, "Invalid relayer fee");
 
         _verifyUpdateDepositMessage(
             depositor,

test/SpokePool.Relay.ts

@@ -303,7 +303,7 @@ async function testUpdatedFeeSignaling(depositorAddress: string) {
     updatedMessage
   );
 
-  // Cannot set new relayer fee pct >= 50%
+  // Cannot set new relayer fee pct >= 50% or <= -50%
   await expect(
     spokePool
       .connect(relayer)
@@ -315,7 +315,19 @@ async function testUpdatedFeeSignaling(depositorAddress: string) {
         updatedMessage,
         signature
       )
-  ).to.be.revertedWith("invalid relayer fee");
+  ).to.be.revertedWith("Invalid relayer fee");
+  await expect(
+    spokePool
+      .connect(relayer)
+      .speedUpDeposit(
+        depositorAddress,
+        toWei("0.5").mul(-1),
+        consts.firstDepositId,
+        updatedRecipient,
+        updatedMessage,
+        signature
+      )
+  ).to.be.revertedWith("Invalid relayer fee");
 
   await expect(
     spokePool