getArtifact function using deprecated (due to security and usability issues) buffer function

[twalshOG]

Describe the bug
Receive a deprecation warning when using downloading an artifact

To Reproduce
Steps to reproduce the behavior:

1. Use the the downloadArtifact functionality in a Github actions pipeline
2. Note you get the following error

(node:1671) [DEP0005] DeprecationWarning: Buffer() is deprecated due to security and usability issues. Please use the Buffer.alloc(), Buffer.allocUnsafe(), or Buffer.from() methods instead.
(Use node --trace-deprecation ... to show where the warning was created)

Code producing the warning

import * as artifact from '@actions/artifact';
.........
  const response = await artifact.default.getArtifact(artifactName);
  const artifactClient = artifact.default;
  await artifactClient.downloadArtifact(response.artifact.id, {
    path: downloadFolder,
  });

Expected behavior
Would not get the error.
This error is due to the fact that @actions/artifact is depending on archiver 5.3.1 which in turn depends on archiver-utils 2.1.0 which use using the depreciated buffer call.

Screenshots

**Where produced **

• Github Actions Agent: ubuntu-latest
• Node version: Default version installed on ubuntu-latest

Additional context
Updating to a new version (3.0.0 or above) would address this issue.
The fix/update to this was already released for archiver-utils.

[TWiStErRob]

To finish the amazing investigation, and give actionable steps for this project:

toolkit/packages/artifact/package.json

Line 52 in 5430c5d

"archiver": "^5.3.1",

The above line needs to be updated from 5.3.1 to at least 6.0.0, which doesn't look like a big jump, as the only breaking change listed is dropping Node 10. 6.0.0 uses archiver-utils 3.0.0.

• (Add Dependabot #1633 would eventually solve this, but there's no reason to wait for that.)

[hubert-rutkowski85]

Bump - it seems like a simple and useful change.