Small fixes for Polish (#1813)

This PR removes two unnecessary rules in Polish. They both make sense
for English (probably someone just copied them from the English file),
but make pronunciation of several Polish words incorrect.

dictsource/pl_rules

         skj (A     S
 
 .group sc
-        sch        S
     pa) sch (a     sx
         sch (abA_  sx
         sch (ab_   sx
 .group	 th
     _e) th (anak   t
      _) the (_     dE
-        th         s
         th (ie_    s;
      _) th         t
      _) thank      fENk