Fix typo in lesson00_standard_library_package

src/content/chapter4_standard_library/lesson00_standard_library_package/en.html

@@ -1,7 +1,7 @@
 <p>
   The Gleam standard library is a regular Gleam package that has been published
   to the <a href="https://hex.pm">Hex</a> package repository. You could opt to
-  not use if you wish, though almost all Gleam projects depend on it.
+  not use it if you wish, though almost all Gleam projects depend on it.
 </p>
 <p>
   All of the modules imported so far in this guide, such as