[v24.2.x] No syntax specified for the proto file Warning

Backport https://github.com/redpanda-data/redpanda/issues/17682 to branch v24.2.x. Requested by PR https://github.com/redpanda-data/redpanda/pull/22633

JIRA Link: [CORE-6752](https://redpandadata.atlassian.net/browse/CORE-6752)