Remove old branch from main_build (#236)

e2e-parallel branch was used for some testing, but shouldn't have been
left to trigger main_build. Cleaning up.

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Author: thpierce

.github/workflows/main_build.yml

@@ -5,7 +5,6 @@ on:
     branches:
       - main
       - "release/v*"
-      - e2e-parallel
 env:
   AWS_DEFAULT_REGION: us-east-1
   STAGING_ECR_REGISTRY: 637423224110.dkr.ecr.us-east-1.amazonaws.com