doc(ford): rm workaround for ford versions < 6.1

Author: Damian Rouson

src/assert_s.F90 src/assert_s.f90src/assert_s.F90 renamed to src/assert_s.f90

@@ -56,11 +56,7 @@
 
     end if toggle_assertions
 
-#ifndef FORD
   contains
-#else
-  end procedure
-#endif
 
     pure function string(numeric) result(number_as_string)
       !! Result is a string represention of the numeric argument
@@ -86,8 +82,6 @@ pure function string(numeric) result(number_as_string)
 
     end function string
 
-#ifndef FORD
   end procedure
-#endif
 
 end submodule