Change Pirate language to en_7S

Since it's English from the seven seas.

Contributes to issue CURA-4263.

.gitignore

@@ -6,7 +6,7 @@ __pycache__
 docs/html
 *.log
 resources/i18n/en_US
-resources/i18n/7s
+resources/i18n/en_7S
 resources/i18n/x-test
 resources/firmware
 resources/materials

resources/qml/Preferences/GeneralPage.qml

@@ -166,7 +166,7 @@ UM.PreferencesPage
                             var date_object = new Date();
                             if (date_object.getUTCMonth() == 8 && date_object.getUTCDate() == 19) //Only add Pirate on the 19th of September.
                             {
-                                append({ text: "Pirate", code: "7s" })
+                                append({ text: "Pirate", code: "en_7S" })
                             }
                         }
                     }