libstdc++: Adjust expected locale-dependent date formats in tests

libstdc++: Adjust expected locale-dependent date formats in tests

The std/time/year_month_day/io.cc test assumes that %x in the fr_FR
locale is %d/%m/%Y but on FreeBSD it is %d.%m.%Y instead. Make the test
PASS for either format.

Similarly, 27_io/manipulators/extended/get_time/char/2.cc expects that
%a in the de_DE locale is "Di" but on FreeBSD it's "Di." with a trailing
period. Adjust the input string to be "1971 Di." instead of "Di 1971"
and that way if %a doesn't expect the trailing '.' it simply won't
extract it from the stream.

This fixes:
FAIL: std/time/year_month_day/io.cc  -std=gnu++20 execution test
FAIL: 27_io/manipulators/extended/get_time/char/2.cc  -std=gnu++17 execution test

libstdc++-v3/ChangeLog:

	* testsuite/27_io/manipulators/extended/get_time/char/2.cc:
	Adjust input string so that it matches %a with or without a
	trailing period.
	* testsuite/std/time/year_month_day/io.cc: Adjust expected
	format for %x in the fr_FR locale.