net: dns: Remove unused variable
net: dns: Remove unused variable

Fix compilation warnings:
...
subsys/net/lib/dns/dns_pack.c:548:6: warning: variable
'remaining_size' set but not used [-Wunused-but-set-variable]
        int remaining_size;
            ^
...

Signed-off-by: Andrei Emeltchenko <a6565233ddc88e4fb9c66c1d70743223493f2ed4@intel.com>

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