Use Document::language_name for the file-type statusline element

The `file-type` indicator element in the statusline was using
`Document::language_id` which is meant to be used to for telling
Language Servers what language we're using. That works for languages
with `language-server` configurations in `languages.toml` but shows
text otherwise. The new `Document::language_name` method from the
parent commit is a more accurate way to determine the language.

helix-term/src/ui/statusline.rs

@@ -329,7 +329,7 @@ fn render_file_type<F>(context: &mut RenderContext, write: F)
 where
     F: Fn(&mut RenderContext, String, Option<Style>) + Copy,
 {
-    let file_type = context.doc.language_id().unwrap_or("text");
+    let file_type = context.doc.language_name().unwrap_or("text");
 
     write(context, format!(" {} ", file_type), None);
 }