Address Dependabot alerts in gRPC for .NET library

[chynesNR]

Some vulnerabilities were found in Grpc.Net.Client by Dependabot:
https://github.com/newrelic/newrelic-dotnet-agent/security/dependabot/70
https://github.com/newrelic/newrelic-dotnet-agent/security/dependabot/68
https://github.com/newrelic/newrelic-dotnet-agent/security/dependabot/69

There is already a fix in the latest version of the library. We just need to update.

Acceptance Criteria

Alerts should close
Integration tests should pass

Estimates

S

[workato-integration]

https://issues.newrelic.com/browse/NR-141374