Run system tests against master with OTP 23 and 24

rabbitmq/rabbitmq-server#3143 enables us to
run system tests against latest rabbitmq-server master ensuring we're
compatible with our Erlang supported versions as documented in
https://www.rabbitmq.com/which-erlang.html

Author: ansd

.github/workflows/pr.yml

@@ -52,7 +52,8 @@ jobs:
         rabbitmq-image:
         - rabbitmq:3.8.8-management
         - rabbitmq:3.8-management
-        - pivotalrabbitmq/rabbitmq:master
+        - pivotalrabbitmq/rabbitmq:master-otp-max
+        - pivotalrabbitmq/rabbitmq:master-otp-max-1
     steps:
     - name: Check out code into the Go module directory
       uses: actions/checkout@v2