Revert "picolibc: Update to version proposed for Zephyr main"

This reverts commit a693b76 because it
pulls in many picolibc patches that are not "absolutely critical" bug
fixes necessary for the SDK 0.17/Zephyr 4.2.

The required bug fix for SDK 0.17/Zephyr 4.2 was already merged in
440cebb.

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio