Reword download index message (#2874)

I'm tired of people thinking the current wording is an error. Improved wordings welcome, this was just my first decent guess.

CHANGELOG.md

@@ -19,6 +19,7 @@ The format is a modified version of [Keep a Changelog](https://keepachangelog.co
 ### Improved
 - Minimize memory usage by reducing in-memory cover cache size ([@Lolle2000la](https://github.com/Lolle2000la)) ([#2266](https://github.com/mihonapp/mihon/pull/2266))
 - Optimize MAL search queries ([@MajorTanya](https://github.com/MajorTanya)) ([#2832](https://github.com/mihonapp/mihon/pull/2832))
+- Reword download reindexing message to avoid confusion ([@MajorTanya](https://github.com/MajorTanya)) ([#2874](https://github.com/mihonapp/mihon/pull/2874))
 
 ### Changed
 - Update tracker icons ([@AntsyLich](https://github.com/AntsyLich)) ([#2773](https://github.com/mihonapp/mihon/pull/2773))

i18n/src/commonMain/moko-resources/base/strings.xml

@@ -609,7 +609,7 @@
     <string name="cookies_cleared">Cookies cleared</string>
     <string name="pref_invalidate_download_cache">Reindex downloads</string>
     <string name="pref_invalidate_download_cache_summary">Force app to recheck downloaded chapters</string>
-    <string name="download_cache_invalidated">Downloads index invalidated</string>
+    <string name="download_cache_invalidated">Recreating download index</string>
     <string name="pref_clear_database">Clear database</string>
     <string name="pref_clear_database_summary">Delete history for entries that are not saved in your library</string>
     <string name="clear_database_source_item_count">%1$d non-library entries in database</string>