net: ip: tcp: use zu format specifier for size_t
net: ip: tcp: use zu format specifier for size_t

The `%i` format specifier is for `int` and is equivalent to
`%d` for printf formatting.

However, for `size_t`, the correct format specifier is `%zu`.

Fixes #49825

Signed-off-by: Christopher Friedt <b335fc22cf1358c7e834a5788f93b9f24396b889@fb.com>

finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr