requirements: update grpcio requirement from <1.42.0 to <1.43.0

Updates the requirements on [grpcio](https://github.com/grpc/grpc) to permit the latest version.
- [Release notes](https://github.com/grpc/grpc/releases)
- [Changelog](https://github.com/grpc/grpc/blob/master/doc/grpc_release_schedule.md)
- [Commits](grpc/grpc@v0.15.0...v1.42.0)

---
updated-dependencies:
- dependency-name: grpcio
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -3,7 +3,7 @@ graph-scheduler>=0.2.0, <1.0.1
 dill<=0.32
 elfi<0.8.3
 graphviz<0.18.0
-grpcio<1.42.0
+grpcio<1.43.0
 grpcio-tools<1.42.0
 llvmlite<0.38
 matplotlib<3.4.4