Update Dapr Bindings Quickstart - .NET

[WhitWaldo]

Description

Dapr package version bump to 1.15.0-rc02. Tweaked program to favor DI registration over the static client builder.

Issue reference

N/A - part of 1.15 endgame

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• The quickstart code compiles correctly
• You've tested new builds of the quickstart if you changed quickstart code
• You've updated the quickstart's README if necessary
• If you have changed the steps for a quickstart be sure that you have updated the automated validation accordingly. All of our quickstarts have annotations that allow them to be executed automatically as code. For more information see mechanical-markdown. For user guide with examples see Examples.

[paulyuk]

LGTM. thank you for this!