Update workflow

Author: mcbridejc

.github/workflows/rust.yml

@@ -1,10 +1,10 @@
-name: Rust
+name: Rust Checks
 
 on:
   push:
-    branches: [ $default-branch ]
+    branches: [ "main"]
   pull_request:
-    branches: [ $default-branch ]
+    branches: [ "main" ]
 
 env:
   CARGO_TERM_COLOR: always