🐛 Fix Lambda.dispose() to return void instead of boolean

Previously, `Lambda.dispose()` returned a boolean value from
`unregister()`, even though its type definition specifies a return type
of `void`. This commit updates the implementation to ensure that
`dispose()` and `[Symbol.dispose]` both return `void` as intended.

Author: Milly

lambda/mod.ts

@@ -265,6 +265,7 @@ export function add(denops: Denops, fn: Fn): Lambda {
   };
   const id = register(denops, fnWrapper);
   const { name } = denops;
+  const dispose = (): void => void unregister(denops, id);
   return {
     id,
     notify: (...args: unknown[]) => {
@@ -275,8 +276,8 @@ export function add(denops: Denops, fn: Fn): Lambda {
       const fnArgs: FnWrapperArgs = [VIM_REQUEST_FLAG, "request", args];
       return expr`eval(denops#request(${name}, ${id}, ${fnArgs}))`;
     },
-    dispose: () => unregister(denops, id),
-    [Symbol.dispose]: () => void unregister(denops, id),
+    dispose,
+    [Symbol.dispose]: dispose,
   };
 }