Remove old upgrade notifications

When updating to v0.6 and v0.7, a notification showed up to explain the
changes. These versions are very old and these notifications are not
expected to be shown again, so this change removes those notifications
and the corresponding strings from messages.json.

Change-Id: I83d4ae901044e176495555da03da48e2f7ffcb16
diff --git a/src/_locales/en/messages.json b/src/_locales/en/messages.json
index 05c6fad..07ffcfb 100644
--- a/src/_locales/en/messages.json
+++ b/src/_locales/en/messages.json
@@ -106,9 +106,5 @@
 		"description": "Cancel button in the dialogs, to reject an action."
 	},
 	"notification_install_title": { "message": "Thanks for installing 'Translate Selected Text'" },
-	"notification_install_message": { "message": "Click this notification to set it up." },
-	"notification_upgradedtostorage_title": { "message": "'Translate Selected Text' was updated to v0.6!" },
-	"notification_upgradedtostorage_message": { "message": "Now your options will be synced across all your devices! The bad side is that you have to set up the extension again :-( Click this notification to set it up." },
-	"notification_reorder_title": { "message": "'Translate Selected Text' was updated to v0.7!" },
-	"notification_reorder_message": { "message": "Now you can configure in which order you want the languages to appear in the context menu. " }
+	"notification_install_message": { "message": "Click this notification to set it up." }
 }