zephyr-env.sh: reduce posixargzero side effects.

For example, when using zsh p9k theme will cause
some problems that affect the experience.

Fixes #20284.

Signed-off-by: Hosun Zhu <hosun@linux.com>

zephyr-env.sh

@@ -17,7 +17,7 @@ if [ -n "${ZSH_VERSION:-}" ]; then
 	if [ $options[posixargzero] != "on" ]; then
 		setopt posixargzero
 		NAME=$(basename -- "$0")
-		setopt posixargzero
+		unsetopt posixargzero
 	else
 		NAME=$(basename -- "$0")
 	fi