gdb/testsuite: remove old comment

gdb/testsuite: remove old comment

In commit:

  commit e92c8eb86dcef673652644694c832c504cf9a9a9
  Date:   Tue Feb 9 15:46:13 2021 +0000

      gdb/fortran: add parser support for lbound and ubound

When I created the test gdb/testsuite/gdb.fortran/lbound-ubound.exp, I
copied the script from a different file and failed to delete the test
description comment at the top (even though I added a new
description).  Fixed in this commit.

gdb/testsuite/ChangeLog:

	* gdb.fortran/lbound-ubound.exp: Remove old comment.