fix(ToggleSwitch): request header correction

[francinelucca]

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What are you trying to accomplish?

Adds X-Requested-with header to ToggleSwitch.

Integration

N/A

List the issues that this change affects.

Closes https://github.com/github/primer/issues/4704

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Merge checklist

• Added/updated tests
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• Tested in Chrome
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🦋 Changeset detected

Latest commit: 6a91bd1

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/view-components	Patch

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[camertron]

After some discussion/research, two things have become apparent:

1. We're already trying to set the right header and I didn't notice 🤦
2. The header we're setting is wrong. It should be X-Requested-With 🤦 🤦

Let's add the X- prefixed header and leave the old one in there too in case someone is relying on it.

Changes addressed