Remove semicolon after TypeScript interface definition (#15827)

## Summary

This PR removes a trailing semicolon after an interface definition in
the custom TypeScript section of `ruff_wasm`. Currently, this semicolon
triggers the error "TS1036: Statements are not allowed in ambient
contexts" when including the file and compiling with e.g `tsc`.

## Test Plan

I made the change, ran `wasm-pack` and copied the generated directory
manually to my `node_modules` folder. I then compiled a file importing
`@astral-sh/ruff-wasm-web` again and confirmed that the compilation
error was gone.

crates/ruff_wasm/src/lib.rs

@@ -53,7 +53,7 @@ export interface Diagnostic {
             };
         }[];
     } | null;
-};
+}
 "#;
 
 #[derive(Serialize, Deserialize, Eq, PartialEq, Debug)]