dx: disable Azure DevOps PR builds (closes #55)

GitHub Actions now handles lint, test, and build on every PR.
Azure DevOps pipeline only needs to run on main pushes to produce
the deploy artifact.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: chrisjwalk-bot

azure-pipelines.yml

@@ -6,6 +6,8 @@
 trigger:
   - main
 
+pr: none
+
 pool:
   vmImage: 'macOS-latest'