Update main_matrix.yml (#2634)

Add Heltec Wireless Paper to S3 Boards

.github/workflows/main_matrix.yml

@@ -85,6 +85,7 @@ jobs:
           - board: heltec-v3
           - board: heltec-wsl-v3
           - board: heltec-wireless-tracker
+          - board: heltec-wireless-paper
           - board: tbeam-s3-core
           - board: tlora-t3s3-v1
     uses: ./.github/workflows/build_esp32_s3.yml