Comment that lint_configuration.md is machine generated

Author: tylerjw

book/src/lint_configuration.md

@@ -1,3 +1,8 @@
+<!--
+This file is generated by `cargo collect-metadata`.
+Please use that command to update the file and do not edit it by hand.
+-->
+
 ## Lint Configuration Options
 | <div style="width:290px">Option</div> | Default Value |
 |--|--|

clippy_lints/src/utils/internal_lints/metadata_collector.rs

@@ -239,7 +239,17 @@ impl Drop for MetadataCollector {
             .create(true)
             .open(MARKDOWN_OUTPUT_FILE)
             .unwrap();
-        writeln!(file, "{}", self.get_markdown_docs(),).unwrap();
+        writeln!(
+            file,
+            "<!--
+This file is generated by `cargo collect-metadata`.
+Please use that command to update the file and do not edit it by hand.
+-->
+
+{}",
+            self.get_markdown_docs(),
+        )
+        .unwrap();
     }
 }