doc(assert_m): fix typo in comment

Author: rouson

src/smart_pointer/assert_m.F90

@@ -15,7 +15,7 @@ module assert_m
 
      pure module subroutine assert(assertion, description)
        !! Error terminate on .false. assertion with the stop code given by description
-       !! With IBM XL Fortran, the stop code is an integer due to for character stop codes being unsupported.
+       !! With IBM XL Fortran, the stop code is an integer due to character stop codes being unsupported.
        implicit none
        logical, intent(in) :: assertion
        character(len=*), intent(in) :: description