Fix the worker-speedtest template (#5830)

[nielsreijers]

The code had been converted to typescript in 026d944, but packages.json and several other places still refered to .js files.

In addition a refactoring of the test code meant tests for both /up and /down urls were now being sent to the handler for /up, causing the tests to fail. I removed some of the test in up.test.ts since they were testing different values of the ?bytes= parameter, but this parameter is only used in down.ts, not in up.ts.

What this PR solves / how to test

Fixes #5830.

Author has addressed the following

• Tests
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  • Included
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• E2E Tests CI Job required? (Use "e2e" label or ask maintainer to run separately)
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• Changeset (Changeset guidelines)
  • TODO (before merge)
  • Included
  • Not necessary because: small change to an example template, not touching main production code
• Public documentation
  • TODO (before merge)
  • Cloudflare docs PR(s): https://github.com/cloudflare/cloudflare-docs/pull/...
  • Not necessary because: bug fix

[changeset-bot]

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Latest commit: f4c937e

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