Update provider version to 4.0.0-preview in AspNetCore package

[abhilasharora]

This pull request updates the reference of the package Microsoft.Extensions.Configuration.AzureAppConfiguration to version 4.0.0-preview.

[jimmyca15]

Just wanted to make sure. We're not doing a preview release of 4.0.0, we're just going straight to stable?

[abhilasharora]

Just wanted to make sure. We're not doing a preview release of 4.0.0, we're just going straight to stable?

Yes, the stable version is needed to unblock the Speech Services Team.

[zhenlan]

I thought we were planning to release a preview first. When was the plan changed?

[abhilasharora]

I thought we were planning to release a preview first. When was the plan changed?

The version upgrade to 4.0.0 stable was already done on June 18 as a part of pull request #174. This was done to ensure the Speech Services Team is unblocked. Let me know if you'd like me to exclude Refresher DI changes or JSON content type changes from this release.

[zhenlan]

We don't need to exclude any changes. We should do a v4 preview release first.

I see there is confusion about what the next release will be. We should start using milestones to track our releases. It helps to clarify what a release will be called and what will be included. I've created a v4.0.0-preview to get us started. Please assign issues that are addressed in upcoming release to it.