Fix mismatch between south and east cases

[Xom]

I discovered this bug after porting your code to GDScript for my game jam game A Bag Deal: https://jamiehello.itch.io/a-bag-deal

This change is a backport to Java. I have not run or tested this Java version, though the change seems straightforward to me.

The bug had caused Player 1 to play EEQUITES in the following screenshot: https://cdn.discordapp.com/attachments/218820487105478657/1127713889115717762/image.png
It happened before Player 2 played RIFLEMAN. EQUITES was already on the board. Player 1's rack was VOIOEII. The word list was CSW22 (279077 words). Note that the bonus placements and tile values are nonstandard.

[Xom]

Actually I think your code might not play EEQUITES anyway, because in my version, I removed some checks from isValidMove() which seemed redundant to me in the circumstances in which it is called, but which might prevent EEQUITES from being played in your version. Separately, my version never had the wrong version of line 270, which seems to me like it may cause some valid moves not to be considered in your version.