chore: Reformat ftl files

Remove trailing whitespace and ensure files end with newlines.

Author: kjarosh

desktop/assets/texts/en-US/about_dialog.ftl

@@ -10,4 +10,4 @@ about-ruffle-commit-time = Commit Time
 about-ruffle-visit-website = Website
 about-ruffle-visit-github = GitHub
 about-ruffle-visit-discord = Discord
-about-ruffle-visit-sponsor = Sponsor
+about-ruffle-visit-sponsor = Sponsor

desktop/assets/texts/en-US/bookmarks_dialog.ftl

@@ -4,4 +4,4 @@ bookmark-dialog-add = Add Bookmark
 bookmarks-dialog-name = Name
 bookmarks-dialog-location = Location
 bookmarks-dialog-no-bookmarks = There are no bookmarks right now
-bookmarks-dialog-not-selected = Nothing to show
+bookmarks-dialog-not-selected = Nothing to show

web/packages/core/texts/en-US/save-manager.ftl

@@ -7,4 +7,4 @@ save-reload-prompt =
 save-download = Download
 save-replace = Replace
 save-delete = Delete
-save-backup-all = Download all save files
+save-backup-all = Download all save files