sys/posix: Correct reference to `core:text/regex`

core/sys/posix/posix.odin

@@ -31,7 +31,7 @@ Unimplemented headers:
 - iso646.h | Impossible
 - math.h | See `core:c/libc`
 - mqueue.h | Targets don't seem to have implemented it
-- regex.h | See `core:regex`
+- regex.h | See `core:text/regex`
 - search.h | Not useful in Odin
 - spawn.h | Use `fork`, `execve`, etc.
 - stdarg.h | See `core:c/libc`