graphics/tulip: fix build on platforms without OpenMP (armv7)

The project tries to include a nonexistent header <tulip/tlphash.h> if
it detects that OpenMP is not supported. Removing the include directive
seems to fix the build; perhaps the header wasn't needed after all.

Approved by: portmgr (build fix blanket)
MFH: 2026Q2

(cherry picked from commit e1a845ecd28830a85731f95597f2dce69307c102)