fix(Proxy): remove unneeded fallback function

https://forum.openzeppelin.com/t/proxy-sol-fallback/36951/8


The fallback alone would indeed be enough.

 Fallback is not limited to` msg.value == 0` (if its marked `payable`). Both functions can support value.

The difference between receive and fallback is in the msg.data. If the calldata is empty and if there is a receive function, it fill be used. Otherwise, fallback is used. This means that regardless of the value, fallback will be called if there is some data. `fallback` is also the one that is called if there is no data, but receive is not defined.

So why do we have a receive function that is not really needed? To silent solidity warnings that sometimes happen when you have a fallback function but no receive function.
- @Amxx 

see <OpenZeppelin/openzeppelin-contracts#4434 (comment)>

Author: sambacha

src/Proxy.sol

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MIT
 // OpenZeppelin Contracts (last updated v4.6.0) (proxy/Proxy.sol)
 
-pragma solidity 0.8.19;
+pragma solidity ^0.8.19;
 
 /**
  * @dev This abstract contract provides a fallback function that delegates all calls to another contract using the EVM
@@ -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.