Fix typos [skip-ci]

Found via codespell v1.17.0.dev0  
``` 
codespell -q 3 -L aci,ake,aline,alle,alledges,alocation,als,ang,anid,ba,beginn,behaviour,bloaded,byteorder,calculater,cancelled,cancelling,cas,cascade,centimetre,childs,colour,colours,commen,connexion,currenty,dof,doubleclick,dum,eiter,elemente,ende,feld,finde,findf,freez,hist,iff,indicies,initialisation,initialise,initialised,initialises,initialisiert,ist,kilometre,lod,mantatory,methode,metres,millimetre,modell,nd,noe,normale,normaly,nto,numer,oder,orgin,orginx,orginy,ot,pard,pres,programm,que,recurrance,rougly,seperator,serie,sinc,strack,substraction,te,thist,thru,tread,uint,unter,vertexes,wallthickness,whitespaces -S ./.git,*.po,*.ts,./ChangeLog.txt,./src/3rdParty,./src/Mod/Assembly/App/opendcm,./src/CXX,./src/zipios++,./src/Base/swig*,./src/Mod/Robot/App/kdl_cp,./src/Mod/Import/App/SCL,./src/WindowsInstaller,./src/Doc/FreeCAD.uml
```

src/Mod/Path/PathScripts/post/heidenhain_post.py

@@ -926,7 +926,7 @@ def HEIDEN_Drill(drill_Obj, drill_Params, drill_Type, drill_feed): # create a dr
         for j in drill_Defs:
             STORED_CANNED_PARAMS[j] = drill_Defs[j]
         
-        # get the DEF template and replace the stings
+        # get the DEF template and replace the strings
         drill_CycleDef = MACHINE_CYCLE_DEF[1].format(
             DIST = str("{:.3f}".format(drill_Defs['DIST'])),
             DEPTH = str("{:.3f}".format(drill_Defs['DEPTH'])),