Fix expected output of gdb.base/line65535.exp with dwarf-5

Fix expected output of gdb.base/line65535.exp with dwarf-5

With gcc & binutils built from latest git revision
this test case fails because the output of the break
command changes and contains the full path name of
the source file, while previously only the file name
was printed.

Fixed that by adjusting the test expectation.

2021-01-22  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	* gdb.base/line65535.exp: Fix test expectation.