Fix typo

Last time I checked, in Gleam, there was no such thing as an `Oction` type ;)

src/content/chapter4_standard_library/lesson04_option_module/text.html

@@ -3,7 +3,7 @@
   <a href="https://hexdocs.pm/gleam_stdlib/gleam/option.html"
     ><code>gleam/option</code></a
   >
-  standard library module defines Gleam's <code>Oction</code> type, which can be
+  standard library module defines Gleam's <code>Option</code> type, which can be
   used to represent a value that is either present or absent.
 </p>