Update mask calculation on TickBitmap::nextInitializedTickWithinOneWord

[ParsaAminpour]

I calculated mask opcode by opcode and realized that calculating mask in this way is slightly gas-efficient.
Based on these test cases

function testMaskAreEqual() public view {
    uint8 bitPos = 8;
    // mask1 function is the calculation that you are currently using.
    uint256 mask1_calculated = mask_cal.mask1(bitPos);
    // mask2 function is the efficient way.
    uint256 mask2_calculated = mask_cal.mask2(bitPos);
    assertEq(mask1_calculated, mask2_calculated);
}
    
function testMask1() public view {
    uint8 bitPos = 8;
    uint256 mask = mask_cal.mask1(bitPos);
    console.log(mask);
}
    
function testMask2() public view {
    uint8 bitPos = 8;
    uint256 mask = mask_cal.mask2(bitPos);
    console.log(mask);
}

The actual functions' code

function mask1(uint8 bitPos) external pure returns(uint256 mask) {
    mask = (1 << bitPos) - 1 + (1 << bitPos);
}
    
function mask2(uint8 bitPos) external pure returns(uint256 mask) {
    mask = (1 << (bitPos+1)) - 1;
}

And the result is (via foundry):

As you can see, there is a small difference in gas consumption between these two functions.