[roll] Roll fuchsia Revert "[starnix] Account for ptr size in execve limits."

This reverts commit c98872bc96287deaece06980c89c5628ae9c868f.

Reason for revert: Likely caused flakiness in minimal.riscv64 builder

Original change's description:
> [starnix] Account for ptr size in execve limits.
>
> In `execve`, there is a limit on the amount of bytes that the argv and
> envp vectors can take. However, that limit has to take into account also
> the size of the pointers that each element will take.
>
> Before this CL, a userspace program could call `execve` with an argument
> vector that if full of the same empty string, and execve would try to
> read each of them, adding 1 byte to the limit count each time, leading
> to OOM.
>
> This change now accounts the size of a pointer for each element added in
> `argv` and `envp`. In `read_c_string_vector` we also count the number of
> elements we are adding and use that towards the total limit size.
>
> Original-Bug: 485312652
> Change-Id: I1ebc58be457965850c365d85e148dbdbb69820cc
> Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1499137
> Reviewed-by: Wez <wez@google.com>
> Commit-Queue: Marco Vanotti <mvanotti@google.com>

Original-Bug: 485312652
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1609250
Exempt: android-build-ayeaye@system.gserviceaccount.com <android-build-ayeaye@system.gserviceaccount.com>
Original-Revision: bb23f1bf81c193360bffc57776bf0c734468b9f9
GitOrigin-RevId: a9e2b0c0c13ad351ea1380e0adbf22ba051cddc8
Change-Id: I8a6a6cfdc0e63783b7bcdeeb4f320f08aad956d4