Remove `isSubgraphCompatible` field from `EnsIndexerConfig`

[tk-o]

Original idea was posted here

We want to begin optimizing more for ENSv2 and the ENS Omnigraph and preparing to leave behind the ENS Subgraph. This idea is also related to the goal of us pushing to get this data model to a place where it is super stable and we don't need to keep breaking it.

[tk-o]

We should always communicate the narrative about Subgraph Compatibility in the most positive way possible.

In other words, it should be either:

• API-level Subgraph Compatibility (API level, but not data level)
• Full Subgraph Compatibility (both API level + data level compatibility)