tsu.sh: add new SU_BINARY_SEARCH path

[AkinaLTS]

Added /debug_ramdisk/su as a location for a new su executable.

In Magisk Alpha b7ca73f4-alpha 28102, the su executable file no longer exists under /system/bin, so executing tsu will result in failure to obtain root privileges. Adding this path allows tsu to work properly. (Commit msg by alpha devs: magisk 和 su 等二进制文件不再硬编码于 /system/bin/目录下，而是从 PATH 环境变量中选择第一个可用位置)

In the original Magisk version 28102, this path also exists and can be used, and therefore it can be considered to have certain universal value.

In the Kitsune Mask, I was unable to test it since my device would not install it (bootloop after install it).

[zixijian]

It is worked. Now termux tsu with magisk 28103

No superuser binary detected.
Are you rooted?

[AkinaLTS]

Termux already provides an alternative. Hence closing.