[patch, committed] Fix trailing space in diagnostic

[Thomas Koenig]

Committed as simple and obvious, 
r10-6802-g7260547dbffd8e6442f99da8adf98ab0ce294e4e.

Regards

        Thomas

    Fix error message.

    2020-02-23  Thomas Koenig  <tkoe...@gcc.gnu.org>

        PR fortran/93890
        * interface.c: Replace "can not" by "cannot" and remove trailing
        space.

    2020-02-23  Thomas Koenig  <tkoe...@gcc.gnu.org>

        PR fortran/93890
        * gfortran.dg/argument_checking_24.f90: Correct test case.