Revert "ethereum: fix view error with newer version of forge"

This reverts commit 05cec3d729 (#3059)

The commit was erroneously included in anticipation of a forge version
update, but it actually only generates an error with an outdated
forge-stdlib version.

The old version's `vm.addr` function
(see
ddb69063e4/src/Vm.sol (L15))
has no `pure` modifier, thus any function using it can not be `pure` (or `view`).
The new version (see
66bf4e2c92/src/Vm.sol (L55))
on the other hand does. In fact, with the new version, removing the
modifier produces a warning.

ethereum/forge-test/TokenImplementation.t.sol

@@ -78,7 +78,7 @@ contract TestTokenImplementation is TokenImplementation, Test {
         address spender,
         uint256 amount,
         uint256 deadline
-    ) public returns (SignatureSetup memory output) {
+    ) public view returns (SignatureSetup memory output) {
         // prepare signer allowing for tokens to be spent
         uint256 sk = uint256(walletPrivateKey);
         output.allower = vm.addr(sk);