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/TechDraw/App/DrawView.cpp

@@ -103,7 +103,7 @@ App::DocumentObjectExecReturn *DrawView::execute(void)
     requestPaint();
     //documentobject::execute doesn't do anything useful for us.
     //documentObject::recompute causes an infinite loop.
-    //should not be neccessary to purgeTouched here, but it prevents a superflous feature recompute
+    //should not be necessary to purgeTouched here, but it prevents a superfluous feature recompute
     purgeTouched();                           //this should not be necessary!
     return App::DocumentObject::StdReturn;
 }