fix: use native token decimals in custom fee token deposit test

The deposit test used parseEther('2') (always 2e18) regardless of the
token's native decimals. Since EthBridger.deposit() passes the amount
directly to depositERC20(uint256) without scaling, this caused failures
for non-18 decimal tokens (16-decimal: exceeds balance, 20-decimal:
value mismatch on L2). These tests were never actually running under
mocha because async describe callbacks aren't awaited.

Author: douglance

.claude/worktrees/agent-a489b965

@@ -0,0 +1 @@
+Subproject commit 2290982e1a5bfe54fca235c077f21c9bc9b75c5a