Remove Strachan reference in header

git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@3814 f3b2605a-c512-4ea7-a41b-209d697bcdaa

examples/reax/ffield.reax

-Reactive MD-force field [Strachan et al, JCP 122 054502 (2005).]                
+Reactive MD-force field
  39       ! Number of general parameters                                        
    50.0000 !Overcoordination parameter                                          
     9.5469 !Overcoordination parameter