chore: bump miniflare to 0.20230628.0

[mrbbot]

What this PR solves / how to test:

This PR bumps and pins miniflare to the latest beta version. This allows us to get a wrangler@beta version with a bunch of workerd fixes, including support for older Linux and macOS versions (#3457), and fixing some memory leaks (#2386).

Associated docs issue(s)/PR(s):

N/A

Author has included the following, where applicable:

• Tests
• Changeset (Changeset guidelines) (we'll make another PR with a changeset once we have a full-release, otherwise we'd have to remove this beta bump changeset)

Reviewer is to perform the following, as applicable:

• Checked for inclusion of relevant tests
• Checked for inclusion of a relevant changeset
• Checked for creation of associated docs updates
• Manually pulled down the changes and spot-tested

[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.devprod.cloudflare.dev/workers-sdk/runs/5421265221/npm-package-wrangler-3544

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

npm install --save-dev https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/prs/3544/npm-package-wrangler-3544

Or you can use npx with this latest build directly:

npx https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/5421265221/npm-package-wrangler-3544 dev path/to/script.js

Additional artifacts:

npm install https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/5421265221/npm-package-cloudflare-pages-shared-3544

Note that these links will no longer work once the GitHub Actions artifact expires.

[codecov]

Codecov Report

Merging #3544 (01fe075) into main (09f317d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #3544   +/-   ##
=======================================
  Coverage   75.09%   75.09%           
=======================================
  Files         190      190           
  Lines       11108    11108           
  Branches     2919     2919           
=======================================
  Hits         8342     8342           
  Misses       2766     2766