libstdc++-v3 expected: Correct minimal-size test in requirements.cc

libstdc++-v3 expected: Correct minimal-size test in requirements.cc

Without this, for a target where alignment and structure-sizes are by
default byte-aligned, such as cris-elf, you'll see, in libstdc++.log:

/X/gcc/libstdc++-v3/testsuite/20_util/expected/requirements.cc:127: error: static assertion failed
/X/gcc/libstdc++-v3/testsuite/20_util/expected/requirements.cc:127: note: the comparison reduces to '(5 == 2)'
compiler exited with status 1
FAIL: 20_util/expected/requirements.cc (test for excess errors)
Excess errors:
/X/gcc/libstdc++-v3/testsuite/20_util/expected/requirements.cc:127: error: static assertion failed

The intent of that line is to check that the object is not larger than
necessary.

libstdc++-v3/:
	* testsuite/20_util/expected/requirements.cc: Correct minimal-size
	test.