revert(engine262): undo Biome formatting changes from b6dbcfe

Restore original formatting in engine262 folder:
- unicode.d.ts: revert to 4-space indentation, single quotes
- syntax-error.d.ts: revert to 4-space indentation, remove semicolons

Biome should not format files in engine262/ as it's excluded in biome.json.

engine262/src/syntax-error.d.ts

@@ -1,5 +1,5 @@
 // eslint-disable-next-line no-unused-vars
 interface SyntaxError {
-  decoration?: string;
-  position?: number;
+    decoration?: string
+    position?: number
 }