fix(docker): proper yum clean up on RHEL8 image creation

Signed-off-by: Raphael Defosseux <raphael.defosseux@openairinterface.org>

docker/Dockerfile.nrf.rhel8

@@ -82,7 +82,8 @@ RUN yum update -y && \
       net-tools \
       procps-ng\
       libevent && \
-    rm -rf /var/lib/apt/lists/*
+    yum clean all -y && \
+    rm -rf /var/cache/yum /var/cache/dnf
 
 # Copying executable and generated libraries
 WORKDIR /openair-nrf/bin