Mk/bsd.gcc.mk: Use GCC 12 in examples

We want to steer people towards current versions of GCC, so use
GCC 12 in examples over GCC 10 and GCC 11 now that the default is
GCC 13.

Mk/bsd.gcc.mk

@@ -22,10 +22,10 @@
 # Examples:
 #   USE_GCC=	yes			# port requires a current version of GCC
 #							# as defined in bsd.default-versions.mk.
-#   USE_GCC=	11 			# port requires GCC 11.
+#   USE_GCC=	12 			# port requires GCC 12.
 #   USE_GCC=	yes:build	# port requires a current version of GCC at
 #							# build time only.
-#   USE_GCC=	10:build	# port requires GCC 10 at build time only.
+#   USE_GCC=	12:build	# port requires GCC 12 at build time only.
 #
 # If you are wondering what your port exactly does, use "make test-gcc"
 # to see some debugging.