Update dependency @nomicfoundation/hardhat-ethers to ^3.1.2

Author: renovate[bot]

backend/package.json

@@ -25,7 +25,7 @@
     "ethers": "6.10.0"
   },
   "devDependencies": {
-    "@nomicfoundation/hardhat-ethers": "^3.0.5",
+    "@nomicfoundation/hardhat-ethers": "^3.1.2",
     "@oasisprotocol/sapphire-contracts": "^0.2.7",
     "@oasisprotocol/sapphire-hardhat": "^2.19.4",
     "@typechain/ethers-v6": "^0.5.1",