This patch marks the nios2*-*-* targets obsolete in GCC 14.  Intel has
EOL'ed this architecture and the maintainers no longer have access to
hardware for testing.  While the port is still in reasonably good
shape at this time, no further testing or updates are planned.

gcc/
	* config.gcc: Add nios2*-*-* to the list of obsoleted targets.

contrib/
	* config-list.mk (LIST): --enable-obsolete for nios2*-*-*.