samples: sockets: big_http_download: Increase stack size to 2.5K.

Testing the sample with Zephyr SDK 1.14 (vs 1.13) with qemu_x86
showed that it consistently crashes on 2th-4th iteration. Avoid
bite-sized increase this time, and dump stack considerably to
avoid constant need to update it.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
1 file changed