chore(generate): add @generated to parser.c header (#4338)

This makes `parser.c` follow the https://generated.at/ convention for generated files. This potentially allows any compatible IDE to discourage editing it directly.

cli/generate/src/render.rs

@@ -330,7 +330,7 @@ impl Generator {
         );
         add_line!(
             self,
-            "/* Automatically generated by tree-sitter v{version} */",
+            "/* Automatically @generated by tree-sitter v{version} */",
         );
         add_line!(self, "");
     }