test: add missing main functions to fixtures

Author: aminya

tests/fixtures/find_impls/src/main.rs

@@ -12,3 +12,5 @@ impl Eq for Bar {}
 
 impl Sub for Foo {}
 impl Super for Foo {}
+
+fn main() {}

tests/fixtures/workspace_symbol_duplicates/src/main.rs

@@ -2,3 +2,5 @@
 mod a;
 #[path="shared.rs"]
 mod b;
+
+fn main() {}