[Certora Audit] G-05. Use iszero instead of eq(*, 0) (#892)

This pull request includes a critical update to the `SafeProxyFactory`
contract in the `contracts/proxies/SafeProxyFactory.sol` file. The
change improves the gas cost of the assembly code by replacing the `eq`
function with the `iszero` function.

Key change:

*
[`contracts/proxies/SafeProxyFactory.sol`](diffhunk://#diff-53aac98a01e16743466b00bdcb233208f95e1113cc90b95181187d9862b4ad6eL43-R43):
Replaced the `eq` function with the `iszero` function in the assembly
block to improve code readability and reliability.

contracts/proxies/SafeProxyFactory.sol

@@ -40,7 +40,7 @@ contract SafeProxyFactory {
             /* solhint-disable no-inline-assembly */
             /// @solidity memory-safe-assembly
             assembly {
-                if eq(call(gas(), proxy, 0, add(initializer, 0x20), mload(initializer), 0, 0), 0) {
+                if iszero(call(gas(), proxy, 0, add(initializer, 0x20), mload(initializer), 0, 0)) {
                     revert(0, 0)
                 }
             }