fix: update reference to highest possible score

Update the explanation of the highest possible score to use the correct 
data source. The change reflects the use of the appropriate language 
object to access the leaderboard's highest possible score.

Author: rohitpaulk

app/components/leaderboard-page/entries-table.ts

@@ -21,7 +21,7 @@ export default class LeaderboardPageEntriesTable extends Component<Signature> {
 
   get explanationMarkdownForScore() {
     return `
-The highest possible score for this track is ${this.args.topEntries[0]!.leaderboard.highestPossibleScore}.
+The highest possible score for this track is ${this.args.language.leaderboard!.highestPossibleScore}.
 
 Harder stages have higher scores assigned to them.
 `.trim();