[infra] Fix Codecov baseline reporting (#2883)

Author: pratstick

.github/workflows/ci.yml

@@ -1,6 +1,8 @@
 name: Build
 
 on:
+  push:
+    branches: [ 'main' ]
   pull_request:
     branches: [ 'main*', 'instrumentation*', 'exporter*', 'extensions*' ]