chore(compiler): make clippy happy

addresses a new lint from Rust 1.76

Author: goto-bus-stop

crates/apollo-compiler/src/validation/mod.rs

@@ -433,8 +433,7 @@ impl DiagnosticList {
 
     pub fn iter(
         &self,
-    ) -> impl Iterator<Item = Diagnostic<'_, DiagnosticData>> + DoubleEndedIterator + ExactSizeIterator
-    {
+    ) -> impl DoubleEndedIterator<Item = Diagnostic<'_, DiagnosticData>> + ExactSizeIterator {
         self.diagnostics_data
             .iter()
             .map(|data| data.to_diagnostic(&self.sources))