I have upgraded Jenkins from version 2.89.4 to 2.121.3

I can see below lines in the logs post upgrade

WARNING: Attempt to (de-)serialize anonymous class hudson.plugins.disk_usage.DiskUsageProjectActionFactory$DescriptorImpl$1 in file
:/var/hudson/master/plugins/disk-usage/WEB-INF/lib/disk-usage.jar; see: https://jenkins.io/redirect/serialization-of-anonymous-clas
ses/
Sep 07, 2018 7:18:40 AM org.jenkinsci.remoting.util.AnonymousClassWarnings warn
WARNING: Attempt to (de-)serialize anonymous class hudson.plugins.disk_usage.DiskUsageOvearallGraphGenerator$DiskUsageRecord$1 in f
ile:/var/hudson/master/plugins/disk-usage/WEB-INF/lib/disk-usage.jar; see: https://jenkins.io/redirect/serialization-of-anonymous-c
lasses/