Add missing Environment Variables for Spring Zeebe SDK

[ana-vinogradova-camunda]

Description

Currently the following Environment Variables are missing from Configuring the Zeebe cluster connection section "Environment variable to be set using this approach" part:

What we currently have:

ZEEBE_AUTHORIZATION_SERVER_URL=xxx
ZEEBE_CLIENT_ID=xxx
ZEEBE_CLIENT_SECRET=xxx

What should be added (here I have example address as well to make sure the customers are aware the the value should be a valid URI that includes schema (http or https):

ZEEBE_GRPC_ADDRESS=http://127.0.0.1:26500/
ZEEBE_REST_ADDRESS=http://127.0.0.1:8083/