Remove nios2-linux-gnu

GCC 15 (e876acab6cdd84bb2b32c98fc69fb0ba29c81153) and binutils
(e7a16d9fd65098045ef5959bf98d990f12314111) both removed all Nios II
support, and the architecture has been EOL'ed by the vendor.  The
kernel still has support, but without a proper compiler there
is no much sense in keep it on glibc.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

scripts/build-many-glibcs.py

@@ -354,9 +354,6 @@ class Context(object):
                                  'ccopts': '-mabi=32'},
                                 {'variant': 'n64',
                                  'ccopts': '-mabi=64'}])
-        self.add_config(arch='nios2',
-                        os_name='linux-gnu',
-                        gcc_cfg=['--enable-obsolete'])
         self.add_config(arch='or1k',
                         os_name='linux-gnu',
                         gcc_cfg=['--with-multilib-list=mcmov,mhard-float'],
@@ -1321,7 +1318,6 @@ def install_linux_headers(policy, cmdlist):
                 'm68k': 'm68k',
                 'microblaze': 'microblaze',
                 'mips': 'mips',
-                'nios2': 'nios2',
                 'or1k': 'openrisc',
                 'powerpc': 'powerpc',
                 's390': 's390',