Add update script for new klipper clear dialog config

Previously, Klipper "clear history" dialog used to not ask again even
if user answered No. This was changed so that only a Yes answer will
lead to no more asking, by using `warningContinueCancel` instead of
`questionYesNo`.

Now the behaviour of previous config value `really_clear_history` has
inverted: true/undefined => ask again; false => don't ask. This update
script migrates old configs to use the new config value, renamed to
`klipperClearHistoryAskAgain`.

Depends on plasma-workspace!816.

CCBUG: 336053

desktoppackage/contents/updates/klipper_clear_config.js

+/*
+ * Previously, Klipper "clear history" dialog used to not ask again even if user answered No.
+ * This was changed so that only a Yes answer will lead to no more asking, by using warningContinueCancel instead of questionYesNo.
+ * Now the behaviour of previous config value really_clear_history has inverted: true/undefined => ask again; false => don't ask.
+ * This update script migrates old configs to use the new config value, renamed to klipperClearHistoryAskAgain.
+*/
+
+config = ConfigFile("plasmashellrc", "Notification Messages");
+oldVal = config.readEntry("really_clear_history");
+if (oldVal === "true") {
+    // Clear and don't ask again -- preserve this choice
+    config.writeEntry("klipperClearHistoryAskAgain", false)
+}
+config.deleteEntry("really_clear_history");