[pmon]: add python3-jsonschema pmon (#8018)

jsonschema is an implementation of JSON Schema for Python .

Signed-off-by: Venkat Garigipati <venkatg@cisco.com>

Author: VenkatCisco

dockers/docker-platform-monitor/Dockerfile.j2

@@ -26,6 +26,7 @@ RUN apt-get update &&   \
         dmidecode       \
         i2c-tools       \
         psmisc          \
+        python3-jsonschema \
         libpci3
 
 # TODO: Remove these lines once we no longer need Python 2