🐛 fix doc test

Since the version is not specified, the latest `[email protected]` is
referenced. However, since this version supports JSR, the following
error occurs in doctest.

```
error: Relative import path "@std/bytes" not prefixed with / or ./ or ../
    at https://deno.land/x/[email protected]/read_all.ts:1:24
```

Author: Milly

client.ts

@@ -21,7 +21,7 @@ type Session = {
  *
  * @example
  * ```ts
- * import { channel } from "https://deno.land/x/streamtools/mod.ts";
+ * import { channel } from "https://deno.land/x/streamtools@v0.5.0/mod.ts";
  * import { Session, Client } from "./mod.ts";
  *
  * const input = channel<Uint8Array>();