Removing FilesSearch feature flag (#17548)

* Removing FilesSearch feature flag

* Fixing tests

* Adding an improvement on plain text extraction

* Adding tests for plain text extraction

* Removed unneeded conversion

* Adding missed license

* Remove the feature flag from the migration

* Fixing some tests

* Updating i18n/en.json file

cmd/mattermost/commands/extract_content.go

@@ -42,7 +42,7 @@ func extractContentCmdF(command *cobra.Command, args []string) error {
 	}
 	defer a.Srv().Shutdown()
 
-	if !*a.Config().FileSettings.ExtractContent || !a.Config().FeatureFlags.FilesSearch {
+	if !*a.Config().FileSettings.ExtractContent {
 		return errors.New("ERROR: Document extraction is not enabled")
 	}