minor #11727 Fix typo in word invitation (CrayD)

This PR was submitted for the 4.3 branch but it was merged into the 4.2 branch instead (closes #11727).

Discussion
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Fix typo in word invitation

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Commits
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108fed6 Fix typo in word invitation

Author: javiereguiluz

translation/message_format.rst

@@ -132,13 +132,13 @@ the function name is ``select`` and its statement contains the "cases" of this
 select. This function is applied over the ``organizer_gender`` variable::
 
     // prints "Ryan has invited you for his party!"
-    echo $translator->trans('invition_title', [
+    echo $translator->trans('invitation_title', [
         'organizer_name' => 'Ryan',
         'organizer_gender' => 'male',
     ]);
 
     // prints "John & Jane have invited you for their party!"
-    echo $translator->trans('invition_title', [
+    echo $translator->trans('invitation_title', [
         'organizer_name' => 'John & Jane',
         'organizer_gender' => 'not_applicable',
     ]);