selftests: net: fix grammar in reuseaddr_ports_exhausted.c log message

This patch fixes a grammatical error in a test log message
in reuseaddr_ports_exhausted.c for better clarity.

Signed-off-by: Pranav Tyagi <pranav.tyagi03@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250213152612.4434-1-pranav.tyagi03@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>