x11-toolkits/gtk30: back out r482635 (undo MFH r482634)

$ make
make: "/usr/ports/x11-toolkits/gtk30/Makefile" line 107: Malformed conditional (${PORT_OPTIONS:MWAYLAND})
make: Fatal errors encountered -- cannot continue
make: stopped in /usr/ports/x11-toolkits/gtk30

Approved by: ports-secteam blanket
Pointy hat to: jbeich (2018Q4 lacks r482189)