std.posix: Fix errno 13 when writing to file

[BryceVandegrift]

Fix to issue #22442

[alexrp]

Can you also update the doc comment here:

zig/lib/std/posix.zig

Lines 1172 to 1174 in b7b46e6

	/// In WASI, this error may occur when the file descriptor does
	/// not hold the required rights to write to it.
	AccessDenied,

[andrewrk]

Thanks!