qt5_graphics: fix copy paste error resulting in incorrect conversion

This just affected the gcode properties calculations.  I have a really 
bad habit of missing the last few characters when copy pasting.. oops.

Author: snowgoer540

src/emc/usr_intf/gremlin/qt5_graphics.py

@@ -462,7 +462,7 @@ def from_internal_units(pos, unit=None):
             if 200 in canon.state.gcodes:
                 units = "in"
                 fmt = "%.4f"
-                conv = 1/25
+                conv = 1/25.4
             else:
                 units = "mm"
                 fmt = "%.3f"