Fix missing font auto complete menu (#1491)

## Launch Checklist

This fixes the position of the autocomplete list - CSS fix mostly.
It also changes the loading of the metadata to be using promises instead
of callbacks.

I couldn't reproduce the following issue, so I'll be closing it for now.
- Fixes #945

Before:
<img width="563" height="577" alt="image"
src="https://github.com/user-attachments/assets/6ea264e1-cb85-4a8a-8df5-ab50e7815333"
/>

After:
<img width="563" height="577" alt="image"
src="https://github.com/user-attachments/assets/27fa2901-dd96-44fd-9774-363fd4c5ed98"
/>


 - [x] Briefly describe the changes in this PR.
 - [x] Link to related issues.
- [x] Include before/after visuals or gifs if this PR includes visual
changes.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/components/App.tsx

@@ -294,13 +294,13 @@ export default class App extends React.Component<any, AppState> {
     const accessToken = metadata["maputnik:openmaptiles_access_token"] || tokens.openmaptiles;
 
     const glyphUrl = (typeof urlTemplate === "string")? urlTemplate.replace("{key}", accessToken): urlTemplate;
-    downloadGlyphsMetadata(glyphUrl, fonts => {
+    downloadGlyphsMetadata(glyphUrl).then(fonts => {
       this.setState({ spec: updateRootSpec(this.state.spec, "glyphs", fonts)});
     });
   }
 
   updateIcons(baseUrl: string) {
-    downloadSpriteMetadata(baseUrl, icons => {
+    downloadSpriteMetadata(baseUrl).then(icons => {
       this.setState({ spec: updateRootSpec(this.state.spec, "sprite", icons)});
     });
   }