specify read permissions for cargo audit

Signed-off-by: Matt Wrock <matt@mattwrock.com>

Author: mwrock

.github/workflows/rust-cargo-audit-check.yml

@@ -2,7 +2,9 @@
 name: Rust Cargo Audit
 on:
   push:
-jobs:
+permissions:
+  contents: read
+  jobs:
   security_audit:
     runs-on: ubuntu-latest
     steps: