Wrong code for changing preferredPlacement 'top-start' to 'bottom-start'

[AlexRom-01]

There's a mistake while checking available space to place tooltip in src/Postel/index.tsx on lines 510-515. If initial value is placement='top-start' it would change to 'bottom-start' and then immediately to 'top-start' again in next check.
https://github.com/timc1/postel/blob/487c063ed845ac11cbba94b29830cb1783c268aa/src/Postel/index.tsx#L510