Remove superfluous receive() function from Proxy.sol (#4434)

Co-authored-by: Francisco Giordano <fg@frang.io>

contracts/proxy/Proxy.sol

@@ -68,14 +68,6 @@ abstract contract Proxy {
         _fallback();
     }
 
-    /**
-     * @dev Fallback function that delegates calls to the address returned by `_implementation()`. Will run if call data
-     * is empty.
-     */
-    receive() external payable virtual {
-        _fallback();
-    }
-
     /**
      * @dev Hook that is called before falling back to the implementation. Can happen as part of a manual `_fallback`
      * call, or as part of the Solidity `fallback` or `receive` functions.