Fix incorrect parse for env binding

[mnixry]

For example

npx wrangler pages dev public/ -b "AAA=foo=bar; foo2=bar2" # actually i want to pass a cookie

It will be parsed to

{
  AAA: 'foo' // all remaining arguments are lost!
}

But it should be parsed to

{
  AAA: 'foo=bar; foo2=bar2' 
}

[changeset-bot]

⚠️ No Changeset found

Latest commit: 00e46e1

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[petebacondarwin]

This looks reasonable to me, but we should get @GregBrimble to make the final decision...

[github-actions]

A wrangler prerelease is available for testing. You can install this latest build in your project with:

npm install --save-dev https://prerelease-registry.developers.workers.dev/runs/1973232754/npm-package-wrangler-581

You can reference the automatically updated head of this PR with:

npm install --save-dev https://prerelease-registry.developers.workers.dev/prs/581/npm-package-wrangler-581

Or you can use npx with this latest build directly:

npx https://prerelease-registry.developers.workers.dev/runs/1973232754/npm-package-wrangler-581 dev path/to/script.js

[GregBrimble]

Thank you, @mnixry, for your contribution!