fix: increase max concurrent resolvers

[StarpTech]

Motivation and Context

Based on our observations in production and feedback from customers, we have concluded that the ENGINE_MAX_CONCURRENT_RESOLVERS value was set too low. Additionally, we have resolved a potential memory issue that we previously misattributed to this limit. A value that is too low can lead to increased latency in subgraph requests due to limited concurrency.

Checklist

• I have discussed my proposed changes in an issue and have received approval to proceed.
• I have followed the coding standards of the project.
• Tests or benchmarks have been added or updated.
• Documentation has been updated on https://github.com/wundergraph/cosmo-docs.
• I have read the Contributors Guide.

[github-actions]

Router image scan passed

✅ No security vulnerabilities found in image:

ghcr.io/wundergraph/cosmo/router:sha-40e4cfa19ddbda071b20b04b48b4061e2a1d7044