typo: remove extraneous "`" in doc comment, fix header (#13848)

* typo: extraneous "`" in doc comment

* Update datafusion/execution/src/runtime_env.rs

* Update datafusion/execution/src/runtime_env.rs

---------

Co-authored-by: Oleks V <[email protected]>

Author: akesling

datafusion/execution/src/runtime_env.rs

@@ -118,9 +118,8 @@ impl RuntimeEnv {
     /// runtime_env.register_object_store(&url, Arc::new(object_store));
     /// ```
     ///
-    /// # Example: Register local file system object store
+    /// # Example: Register remote URL object store like [Github](https://github.com)
     ///
-    /// To register reading from urls such as <https://github.com>`
     ///
     /// ```
     /// # use std::sync::Arc;