posix: remove the is_temp things that prevented use-after-frees

https://github.com/odin-lang/Odin/commit/d0709a7de21efded4625167dbff4a7dd13d561b4
fixes those another way.

core/os/os2/file_posix.odin

@@ -191,7 +191,7 @@ _symlink :: proc(old_name, new_name: string) -> Error {
 }
 
 _read_link :: proc(name: string, allocator: runtime.Allocator) -> (s: string, err: Error) {
-	TEMP_ALLOCATOR_GUARD(ignore=is_temp(allocator))
+	TEMP_ALLOCATOR_GUARD()
 	cname := temp_cstring(name)
 
 	buf: [dynamic]byte