Store new config on application in :config-reload (#5431)

After changes in #5239, the loaded configuration wasn't stored,
resulting in a success message even if the instance kept the previous
configuration values.

helix-term/src/application.rs

@@ -436,6 +436,8 @@ impl Application {
                 .map_err(|err| anyhow::anyhow!("Failed to load config: {}", err))?;
             self.refresh_language_config()?;
             self.refresh_theme(&default_config)?;
+            // Store new config
+            self.config.store(Arc::new(default_config));
             Ok(())
         };