Add note to printer profile editor about offsets

We don't need to define them in the firmware AND in OctoPrint. If they
are already set in firmware we'll otherwise get wonky issues in the
GCODE viewer or when slicing.

Closes #2229

src/octoprint/templates/snippets/settings/printerprofiles/profileEditorExtruder.jinja2

@@ -27,7 +27,7 @@
         <div data-bind="visible: !sharedNozzle()" style="display: none">
             <div class="control-group">
                 <div class="controls">
-                    {{ _('Please specify the nozzle offsets of the extruders relative to the first nozzle T0.') }}
+                    {{ _('Please specify the nozzle offsets of the extruders relative to the first nozzle T0 <strong>if you haven\'t already done so in your firmware</strong>. Otherwise leave them at (0,0).') }}
                 </div>
             </div>