Typo error in documentation.

[chas2706]

@dc42
Have just noticed this typo error in the Gcode documentation:

M851: Set Z-Probe Offset (Marlin Compatibility)
RepRapFirmware 2.02 and later

M851 Znn is implemented for backwards compatibility with other firmware. It sets the Z probe trigger in the same way as G31 Z-nn (note the sign reversal). It also flags the Z-probe G31 parameters as to be saved in config-override.g if the M500 command is used.

G31 should be used in preference to M581.

Obviously it should refer to M851 not M581.

[droftarts]

@chas2706 Thanks, fixed.

Ian