update requirements needed for plan contour plotting (#71)

requirements.txt

@@ -4,7 +4,7 @@ certifi==2020.11.8
 cycler==0.10.0
 Cython==0.29.21
 decorator==4.4.2
-gcode2contour @ git+https://code.research.uts.edu.au/bigprint/gcode2contour.git@defe7cf5eefe80e4dda02a7d051d22245402aa2a
+gcode2contour @ git+https://code.research.uts.edu.au/bigprint/gcode2contour.git@0994d925e897343dd526cb4161946f88c839f7c8
 ipython==7.19.0
 ipython-genutils==0.2.0
 jedi==0.17.2