Protobuf and gRPC Version Updates for Python 3.9 - 3.12

## Summary

Due to a critical security vulnerability ([CVE-2026-0994](https://nvd.nist.gov/vuln/detail/CVE-2026-0994)) discovered in `protobuf` versions prior to 5.29.6, we are updating the `protobuf` and `grpcio` dependencies in the Python Worker. This update will be rolled out with host version **4.1052** and may cause breaking changes for some Python function apps.

## What's Changing

The following dependency versions are being updated in the Azure Functions Python Worker:

- **protobuf**: `~=4.25.3` → `~=5.29.6`
- **grpcio**: `~=1.59.0` → `~=1.70.0`

## Who Is Affected

This change may affect you if:

- Your Python function app uses `protobuf` or `grpcio` directly in your code or dependencies
- Your app runs on **Python 3.9, 3.10, 3.11, or 3.12**
- You have pinned specific versions of `protobuf` or `grpcio` in your `requirements.txt` that are incompatible with the new versions

## Rollout Timeline

- **Host Version**: 4.1052
- **Expected Completion**: August 2026

## Potential Impact

After this update is deployed, function apps that depend on older versions of `protobuf` or `grpcio` may experience:

- Runtime errors or import failures
- Type incompatibilities if using protobuf-generated code compiled with older versions
- Breaking changes in gRPC functionality due to API changes between major versions

```
RuntimeError: The grpc package installed is at version 1.37.1, but the generated code in
FunctionRpc_pb2_grpc.py depends on grpcio>=1.70.0.
```

## Mitigation Options

### Option 1: Update Your Dependencies

Update your `requirements.txt` to use compatible versions:

```txt
protobuf~=5.29.6
grpcio~=1.70.0
```

### Option 2: Use Isolated Worker Dependencies

If you need to continue using older versions of `protobuf` or `grpcio`, you can set the `PYTHON_ISOLATE_WORKER_DEPENDENCIES` application setting to `1` to prioritize your app's pinned versions.

### Option 3: Migrate to Python >= 3.13

Migrate your existing function apps to run on Python 3.13 or Python 3.14.