Fix missing code blocks in GDScript exports (#5998)

tutorials/scripting/gdscript/gdscript_exports.rst

@@ -66,6 +66,8 @@ the following to list them:
 
 Integers and strings hint enumerated values.
 
+::
+
     # Editor will enumerate as 0, 1 and 2.
     @export_enum("Warrior", "Magician", "Thief") var character_class
 
@@ -213,6 +215,8 @@ Opening the inspector dropdown may result in an
 extremely long list of possible classes to create, however.
 Therefore, if you specify an extension of Resource such as:
 
+::
+
     @export var resource: AnimationNode
 
 The drop-down menu will be limited to AnimationNode and all