Remove Polish translation option

The translator said he won't be maintaining this language any more. Someone else can pick it up now if he wants to, but we'll disable the language until it is complete again.

Contributes to issue CURA-5451.

resources/qml/Preferences/GeneralPage.qml

@@ -170,7 +170,7 @@ UM.PreferencesPage
                             append({ text: "日本語", code: "ja_JP" })
                             append({ text: "한국어", code: "ko_KR" })
                             append({ text: "Nederlands", code: "nl_NL" })
-                            append({ text: "Polski", code: "pl_PL" })
+                            //Polish is disabled for being incomplete: append({ text: "Polski", code: "pl_PL" })
                             append({ text: "Português do Brasil", code: "pt_BR" })
                             append({ text: "Português", code: "pt_PT" })
                             append({ text: "Русский", code: "ru_RU" })