Add `view` modifier to `proxyAdmin` in TransparentUpgradeableProxy (#4688)

Co-authored-by: Eric Lau <ericglau@outlook.com>

.changeset/eleven-planets-relax.md

@@ -0,0 +1,5 @@
+---
+'openzeppelin-solidity': patch
+---
+
+`TransparentUpgradeableProxy`: Make internal `_proxyAdmin()` getter have `view` visibility.

contracts/proxy/transparent/TransparentUpgradeableProxy.sol

@@ -50,7 +50,7 @@ interface ITransparentUpgradeableProxy is IERC1967 {
  * IMPORTANT: This contract avoids unnecessary storage reads by setting the admin only during construction as an
  * immutable variable, preventing any changes thereafter. However, the admin slot defined in ERC-1967 can still be
  * overwritten by the implementation logic pointed to by this proxy. In such cases, the contract may end up in an
- * undesirable state where the admin slot is different from the actual admin. Relying in the value of the admin slot
+ * undesirable state where the admin slot is different from the actual admin. Relying on the value of the admin slot
  * is generally fine if the implementation is trusted.
  *
  * WARNING: It is not recommended to extend this contract to add additional external functions. If you do so, the
@@ -84,7 +84,7 @@ contract TransparentUpgradeableProxy is ERC1967Proxy {
     /**
      * @dev Returns the admin of this proxy.
      */
-    function _proxyAdmin() internal virtual returns (address) {
+    function _proxyAdmin() internal view virtual returns (address) {
         return _admin;
     }