contracts-bedrock: fix compiler warnings

Fix the compiler warnings in the `DelayedVetoable` tests.
There were unused variables returned from low level calls.
There are alternative compiler warning if there is no
assignment to the variables, so the solution is to use them
either in an assertion or just reference them on their own line.
Silly compiler.

packages/contracts-bedrock/.gas-snapshot

@@ -47,8 +47,8 @@ CrossDomainOwnableThroughPortal_Test:test_depositTransaction_crossDomainOwner_su
 CrossDomainOwnable_Test:test_onlyOwner_notOwner_reverts() (gas: 10597)
 CrossDomainOwnable_Test:test_onlyOwner_succeeds() (gas: 34883)
 DelayedVetoable_Getters_Test:test_getters() (gas: 24466)
-DelayedVetoable_Getters_TestFail:test_getters_notZeroAddress_reverts() (gas: 31166)
-DelayedVetoable_HandleCall_TestFail:test_handleCall_unauthorizedInitiation_reverts() (gas: 20234)
+DelayedVetoable_Getters_TestFail:test_getters_notZeroAddress_reverts() (gas: 31206)
+DelayedVetoable_HandleCall_TestFail:test_handleCall_unauthorizedInitiation_reverts() (gas: 20291)
 DeleteOutput:test_script_succeeds() (gas: 3100)
 DeployerWhitelist_Test:test_owner_succeeds() (gas: 7582)
 DeployerWhitelist_Test:test_storageSlots_succeeds() (gas: 33395)

packages/contracts-bedrock/test/DelayedVetoable.t.sol

@@ -32,6 +32,7 @@ contract DelayedVetoable_Init is CommonTest {
         // value in storage.
         vm.prank(initiator);
         (bool success,) = address(delayedVetoable).call(hex"");
+        assertTrue(success);
     }
 
     /// @dev This function is used to prevent initiating the delay unintentionally.
@@ -146,6 +147,7 @@ contract DelayedVetoable_HandleCall_TestFail is DelayedVetoable_Init {
     function test_handleCall_unauthorizedInitiation_reverts() external {
         vm.expectRevert(abi.encodeWithSelector(Unauthorized.selector, initiator, address(this)));
         (bool success,) = address(delayedVetoable).call(NON_ZERO_DATA);
+        assertTrue(success);
     }
 
     /// @dev The call cannot be forwarded until the delay has passed.
@@ -156,6 +158,7 @@ contract DelayedVetoable_HandleCall_TestFail is DelayedVetoable_Init {
 
         vm.expectRevert(abi.encodeWithSelector(ForwardingEarly.selector));
         (success,) = address(delayedVetoable).call(data);
+        success;
     }
 
     /// @dev The call cannot be forwarded a second time.
@@ -165,6 +168,7 @@ contract DelayedVetoable_HandleCall_TestFail is DelayedVetoable_Init {
         // Initiate the call
         vm.prank(initiator);
         (bool success,) = address(delayedVetoable).call(data);
+        assertTrue(success);
 
         vm.warp(block.timestamp + operatingDelay);
         vm.expectEmit(true, false, false, true, address(delayedVetoable));
@@ -193,6 +197,7 @@ contract DelayedVetoable_HandleCall_TestFail is DelayedVetoable_Init {
         // Initiate the call
         vm.prank(initiator);
         (bool success,) = address(delayedVetoable).call(inData);
+        success;
 
         vm.warp(block.timestamp + operatingDelay);
         vm.expectEmit(true, false, false, true, address(delayedVetoable));
@@ -203,6 +208,7 @@ contract DelayedVetoable_HandleCall_TestFail is DelayedVetoable_Init {
         // Forward the call
         vm.expectRevert(outData);
         (bool success2,) = address(delayedVetoable).call(inData);
+        success2;
     }
 
     /// @dev A test documenting the single instance in which the contract is not 'transparent' to the initiator.
@@ -217,5 +223,6 @@ contract DelayedVetoable_HandleCall_TestFail is DelayedVetoable_Init {
         vm.prank(initiator);
         vm.expectRevert(outData);
         (bool success,) = address(delayedVetoable).call(inData);
+        success;
     }
 }