GRPC logger produces excessive noise at INFO level

### Problem
The GRPC logger, initialized in [`common/flogging/global.go:31`](https://github.com/hyperledger/fabric-lib-go/blob/ac15a5b13196483c466032a2ea6c663fc0ea7481/common/flogging/global.go#L31), generates excessive log output even at INFO level. This creates significant noise in application logs, making it difficult to identify relevant application-level information.

### Impact
- Log files become cluttered with GRPC internal messages
- Harder to debug application-level issues
- Increased log storage requirements
- Reduced log readability

### Proposed Solution
Change the default GRPC logger level to ERROR.

### Benefits
- Cleaner default log output
- Maintains ability to enable verbose GRPC logging for debugging
- Follows principle of least surprise - most users don't need GRPC internal logs
- Backward compatible - applications can opt-in to verbose GRPC logging

### Related Projects
This issue affects all projects that depend on fabric-lib-go, including:
- Fabric-X
- Fabric
- Other Hyperledger Fabric components