Run unit tests on the main branch (#3126)

Signed-off-by: shuheiktgw <s-kitagawa@mercari.com>

.github/workflows/ci.yml

@@ -96,7 +96,7 @@ jobs:
   unit-tests:
     runs-on: ubuntu-latest
     needs: detect-noop
-    if: needs.detect-noop.outputs.noop != 'true' && github.ref != 'refs/heads/main'
+    if: needs.detect-noop.outputs.noop != 'true'
 
     steps:
       - name: Checkout