Update lint name to follow convention

src/test/rustdoc-ui/no-crate-level-doc-lint.rs

@@ -1,3 +1,3 @@
-#![deny(missing_crate_level_doc)]
+#![deny(missing_crate_level_docs)]
 
 pub fn foo() {}

src/test/rustdoc-ui/no-crate-level-doc-lint.stderr

@@ -3,8 +3,8 @@ error: no documentation found for this crate's top-level module
 note: the lint level is defined here
   --> $DIR/no-crate-level-doc-lint.rs:1:9
    |
-LL | #![deny(missing_crate_level_doc)]
-   |         ^^^^^^^^^^^^^^^^^^^^^^^
+LL | #![deny(missing_crate_level_docs)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^
    = help: The following guide may be of use:
            https://doc.rust-lang.org/nightly/rustdoc/how-to-write-documentation.html