Downgrade ethers.js to 5.6.1 in ens, gnosis, euler, perpetual-pools and uniswap external tests

test/externalTests/uniswap.sh

@@ -77,6 +77,10 @@ function uniswap_test
     yarn install
     yarn add hardhat-gas-reporter
 
+    # With ethers.js 5.6.2 many tests for revert messages fail.
+    # TODO: Remove when https://github.com/ethers-io/ethers.js/discussions/2849 is resolved.
+    yarn add ethers@5.6.1
+
     replace_version_pragmas
 
     for preset in $SELECTED_PRESETS; do