fix: mention only the PR description is generated (#25)

Author: sgoudham

dist/index.js

@@ -3,7 +3,7 @@ import { Submodule } from "./main";
 const header = () => "This PR updates the following submodules:";
 
 const footer = () =>
-  "---\n\nThis PR was generated by [sgoudham/update-git-submodules](https://github.com/sgoudham/update-git-submodules).";
+  "---\n\nThis PR description was generated by [sgoudham/update-git-submodules](https://github.com/sgoudham/update-git-submodules).";
 
 const tableHeader = () =>
   "| **Remote Repository** | **Submodule Path** | **Change** |\n| --- | --- | --- |";