Fix CI syntax

Author: orottier

.github/workflows/rust.yml

@@ -14,7 +14,6 @@ env:
 jobs:
   verify-build:
     runs-on: ubuntu-latest
-    if: github.ref != 'refs/heads/main'
 
     steps:
     # checkout repo
@@ -56,6 +55,9 @@ jobs:
 
   benchmark:
     runs-on: ubuntu-latest
+    if: github.ref != 'refs/heads/main'
+
+    steps:
     # checkout repo, install dependencies
     - uses: actions/checkout@v3
       with: