getBase64() does not return as proper base64 in Deno Deploy

# Expected Behavior

When running getBase64() I expect to get a proper base64 string. It does this in local Deno, but not on Deno Deploy.

# Current Behavior

Somehow the same function on Deno Deploy just returns a comma-separated set of numbers between 0 and 255, like this:

```
data:image/jpeg;base64,255,216,255,224,0,16,74,70,73,70,0,1,1,0,0,1,0,1,0,0,255,219,0,132,0,6,4,5,6,5,4,6,6,5,6,7,7,6,8,10,16,10,10,9,9,10,20,14,15,12,16,23,20,24,24,23,20,22,22,26,29,37,31,26,27,35,28,22,22,32,44,32,35,38,39,41,42,41,25,31,45,48,45,40,48,37,40,41,40,1,7,7,7,10,8,10,19,10,10,19,40,26,22,26,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40 ...
```

# Failure Information (for bugs)

## Steps to Reproduce

It happens on all images; this is an Astro action where a form has a file upload. Fairly vanilla:
And it does NOT do this on local Astro running on Deno. For some reason this is ONLY on Deno Deploy. I have no idea why.

```
const image = await Jimp.fromBuffer(imgBuffer);
const resizedImgBuffer = await image.resize({w: 300}).getBase64(data.profileImage.type, {quality: 80});
console.log("Output:", resizedImgBuffer);
```

## Context

Again, no idea why this happens on Deno Deploy. However, if I use getBuffer, and then convert to base64, it's fine.

On Deno I do get a warning that `This browser lacks typed array (Uint8Array) support which is required by `buffer` v5.x. Use `buffer` v4.x if you require old browser support.` — maybe this has something to do with it, or not at all?

```
import { Buffer } from 'node:buffer';
const image = await Jimp.fromBuffer(imgBuffer);
const resizedImgBuffer = await image.resize({w: 300}).getBuffer(data.profileImage.type, {quality: 80});
data.profileImage.data = Buffer.from(resizedImgBuffer).toString('base64');
```

- Jimp Version: 1.6.0
- Operating System: Mac Sonoma / Deno Deploy
- Node version: Deno 2.1.9

## Failure Logs

None; it doesn't error, it just generates a list of numbers.