sector_mines.inc.php: fix undefined function call
sector_mines.inc.php: fix undefined function call

The `SmrShip::getShipClassID` method was renamed `SmrShip::getClassID`
in 890a2a83f6.

hemberger/smr,hemberger/smr,smrealms/smr,smrealms/smr,smrealms/smr,hemberger/smr,hemberger/smr