fix: upgrade minimum rigo token interfaces solc

- minimum solc 0.8.0 required to prevent rogue rollback which skips safe math default checks

contracts/rigoToken/interfaces/IInflation.sol

@@ -17,7 +17,7 @@
 
 */
 
-pragma solidity >=0.4.22 <0.9.0;
+pragma solidity >=0.8.0 <0.9.0;
 
 /// @title Inflation Interface - Allows interaction with the Inflation contract.
 /// @author Gabriele Rigo - <gab@rigoblock.com>

contracts/rigoToken/interfaces/IProofOfPerformance.sol

@@ -17,7 +17,7 @@
 
 */
 
-pragma solidity >=0.4.22 <0.9.0;
+pragma solidity >=0.8.0 <0.9.0;
 
 /// @title Proof of Performance Interface - Allows interaction with the PoP contract.
 /// @author Gabriele Rigo - <gab@rigoblock.com>

contracts/rigoToken/interfaces/IRigoToken.sol

@@ -17,7 +17,7 @@
 
 */
 
-pragma solidity >=0.5.0 <0.9.0;
+pragma solidity >=0.8.0 <0.9.0;
 
 import "../../tokens/ERC20/IERC20.sol";