Remove dead code

[jecaro]

This dead code makes the compilation fail on my system with:

/home/jcquillet/development/badgeware-simulator/src/font.cpp: In member function ‘picovector::rect_t picovector::font_t::measure(picovector::image_t*, const char*, float)’:
/home/jcquillet/development/badgeware-simulator/src/font.cpp:50:18: error: variable ‘b’ set but not used [-Werror=unused-but-set-variable]
   50 |           rect_t b = this->glyphs[j].bounds(&transform);
      |                  ^