Fix std::wstring allocator tests

Fix std::wstring allocator tests

	* testsuite/21_strings/basic_string/allocator/wchar_t/copy.cc:
	Remove reundant check for _GLIBCXX_USE_WCHAR_T and fix char type.
	* testsuite/21_strings/basic_string/allocator/wchar_t/copy_assign.cc:
	Likewise.
	* testsuite/21_strings/basic_string/allocator/wchar_t/minimal.cc:
	Likewise.
	* testsuite/21_strings/basic_string/allocator/wchar_t/move.cc:
	Likewise.
	* testsuite/21_strings/basic_string/allocator/wchar_t/move_assign.cc:
	Likewise.
	* testsuite/21_strings/basic_string/allocator/wchar_t/noexcept.cc:
	Likewise.
	* testsuite/21_strings/basic_string/allocator/wchar_t/swap.cc:
	Likewise.

From-SVN: r238996