Fix security audit github action (#1256)

This fixes the Security Audit github workflow by consolidating the two
separte yaml documents that Github Actions didn't like into a single
workflow with multiple triggers. I also added a trigger for PRs as well
as pushes.

.github/workflows/security_audit.yml

@@ -1,22 +1,14 @@
 ---
 name: Security audit
 on:
+  pull_request:
+    paths:
+      - '**/Cargo.toml'
+      - '**/Cargo.lock'
   push:
     paths:
       - '**/Cargo.toml'
       - '**/Cargo.lock'
-jobs:
-  security_audit:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v1
-      - uses: actions-rs/audit-check@v1
-        with:
-          token: ${{ secrets.GITHUB_TOKEN }}
-
----
-name: Security audit [Daily]
-on:
   schedule:
     - cron: '0 0 * * *'
 jobs: