Fix Deno KV errors in the latest deno

[Shougo]

% deno --version
deno 1.40.4 (release, x86_64-unknown-linux-gnu)
v8 12.1.285.6
typescript 5.3.3

Deno 最新版で補完を使うとエラーが出ていたので修正。

[ddc] source: skkeleton "gather()" failed
[ddc] unknown error object
[denops] TypeError: start key is not in the keyspace defined by prefix
[denops]     at KvListIterator.<anonymous> (ext:deno_kv/01_db.ts:141:36)
[denops]     at KvListIterator.next (ext:deno_kv/01_db.ts:579:42)
[denops]     at Dictionary.getCompletionResult (file:///home/shougo/work/skkeleton/denops/skkeleton/sources/deno_kv.ts:138:15)
[denops]     at NumberConvertWrapper.getCompletionResult (file:///home/shougo/work/skkeleton/denops/skkeleton/dictionary.ts:163:42)
[denops]     at Library.getCompletionResult (file:///home/shougo/work/skkeleton/denops/skkeleton/dictionary.ts:248:21)
[denops]     at eventLoopTick (ext:core/01_core.js:65:7)
[denops]     at async Plugin.call (file:///home/shougo/work/denops.vim/denops/@denops-private/service.ts:139:12)
[denops]     at async Service.#dispatch (file:///home/shougo/work/denops.vim/denops/@denops-private/service.ts:69:12)
[denops]     at async Service.dispatch (file:///home/shougo/work/denops.vim/denops/@denops-private/service.ts:74:14)
[denops]     at async Source.gather (file:///home/shougo/work/skkeleton/denops/@ddc-sources/skkeleton.ts:33:25)