nac3core: fix typo and remove the unnecessary 'return' statement

nac3core/src/toplevel/composer.rs

@@ -37,7 +37,7 @@ pub struct TopLevelComposer {
     // number of built-in function and classes in the definition list, later skip
     pub builtin_num: usize,
     pub core_config: ComposerConfig,
-    // the class name and it's constructor function
+    // the class name and its constructor function
     pub constructor_lookup: HashMap<StrRef, ast::Located<ast::StmtKind>>,
 }
 
@@ -185,7 +185,7 @@ impl TopLevelComposer {
                         return Some((**class_name, stmt.clone()))
                     }
                 }
-                return None
+                None
             })
         );