Publishing to Beanstalk on Linux with no keypair uses a keypair called LinuxBeanstalk

**Describe the bug**
When publishing a .net core application to Beanstalk, using a Linux container type, and choosing No key pair for the key pair, the deployment tries to use a key called LinuxBeanstalk, generating error if key pair does not exist.

**To Reproduce**
1. Load a .net core application
2. Right-click on it, and select publish to AWS Elastic Beanstalk
3. Choose credentials, and select Create a new application environment, then click next
4. Choose an application name and environment, click next
5. Choose 64bit Amazon Linux 2 v2.1.5 running .Net core for container type, select an appropriate instance type, and select for Key pair. Click Next
6. Click Next twice, for permissions and options.
7. Choose Deploy

**Expected behavior**
A new Beanstalk environment is created, my application is deployed

**Screenshots**

**Computer (please complete the following information):**
- Windows Version: 10 Enterprise, Version 10.0.19042 Build 19042
- Visual Studio Version: Pro 2019, Version 16.9.5
- AWS Toolkit for Visual Studio Version: 1.21.1.0

**Additional context**
This is causing problems, among other things, with a published AWS training course, as referenced in forums: https://forums.aws.amazon.com/thread.jspa?messageID=983954󰎒

Start by reproducing the deployment in Visual Studio 2019 with AWS Toolkit 1.21.1.0, using a .NET Core application, Amazon Linux 2 .NET Core container, and . Trace the Elastic Beanstalk deployment entry point to find why LinuxBeanstalk is selected, then verify that deployment succeeds without requiring a key pair.

Written by the indexing model from the issue text.