fix: don't fetch migrations when in --dry-run mode

[threepointone]

Fixes #1038

[changeset-bot]

🦋 Changeset detected

Latest commit: e4c0c42

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

This PR includes changesets to release 1 package

Name	Type
wrangler	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[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/2337549688/npm-package-wrangler-1039

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

npm install --save-dev https://prerelease-registry.developers.workers.dev/prs/1039/npm-package-wrangler-1039

Or you can use npx with this latest build directly:

npx https://prerelease-registry.developers.workers.dev/runs/2337549688/npm-package-wrangler-1039 dev path/to/script.js

[rozenmd]

LGTM 👍