Fix `Charts / install` CI workflow after Read-Only feature

[acuarica]

The introduction of this PR #3896 makes the Charts / install CI workflow to fail. The error is the following

Error: Configuration error: OPERATOR_ID_MAIN is mandatory for Relay operations in Read-Write mode.

https://github.com/hiero-ledger/hiero-json-rpc-relay/actions/runs/16170821472/job/45643616341#step:14:1537

Fix the charts configuration to enable this workflow to work properly.