safeApprove of openZeppelin is deprecated

[code423n4]

Handle

robee

Vulnerability details

You use safeApprove of openZeppelin although it's deprecated.
(see https://github.com/OpenZeppelin/openzeppelin-contracts/blob/566a774222707e424896c0c390a84dc3c13bdcb2/contracts/token/ERC20/utils/SafeERC20.sol#L38)
You should change it to increase/decrease Allowance as OpenZeppilin says.
This appears in the following locations in the code base:

    Deprecated safeApprove in RebalanceManager.sol line 83: IERC20(swap.tokenIn).approve.selector, 
    Deprecated safeApprove in RebalanceManager.sol line 130: IERC20(swap.path[0]).approve.selector, 
    Deprecated safeApprove in RebalanceManagerV2.sol line 69: IERC20(swap.path[0]).approve.selector, 
    Deprecated safeApprove in RebalanceManagerV3.sol line 74: IERC20(path[0]).approve.selector, 
    Deprecated safeApprove in SingleNativeTokenExit.sol line 43: token.approve(spender, uint256(-1)); 
    Deprecated safeApprove in SingleNativeTokenExitV2.sol line 54: token.approve(spender, uint256(-1)); 
    Deprecated safeApprove in SingleTokenJoin.sol line 42: token.approve(spender, uint256(-1)); 
    Deprecated safeApprove in SingleTokenJoinV2.sol line 52: token.approve(spender, uint256(-1)); 

[0xleastwood]

No direct security risk, so marking as non-critical.