[monitoring-plugins] Install libjson-perl in test runner

[Lorenz Kästle]

 Module: monitoring-plugins
 Branch: master
 Commit: 7d378949670fa8941d14f78e0279992f390bcd2c
 Author: Lorenz Kästle <12514511+RincewindsHat at users.noreply.github.com>
   Date: Wed Feb 19 17:32:56 2025 +0100
    URL: https://www.monitoring-plugins.org/repositories/monitoring-plugins/commit/?id=7d378949

Install libjson-perl in test runner

---

 .github/prepare_debian.sh | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/.github/prepare_debian.sh b/.github/prepare_debian.sh
index 3640e500..c79211cd 100755
--- a/.github/prepare_debian.sh
+++ b/.github/prepare_debian.sh
@@ -61,7 +61,8 @@ apt-get -y install perl \
 	libmariadb-dev \
 	cron \
 	iputils-ping \
-	iproute2
+	iproute2 \
+	libjson-perl
 
 # remove ipv6 interface from hosts
 sed '/^::1/d' /etc/hosts > /tmp/hosts