fix: ee server not reachable behind a proxy

[mattinannt]

What does this PR do?

The ee license check is currently not working when Formbricks is used behind a proxy. This PR introduces a switch from fetch to axios to respect the proxy settings set via environment variables HTTP_PROXY & HTTPS_PROXY.

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2 Ignored Deployments

| Name | Status | Preview | Comments | Updated (UTC) | | :--- | :----- | :------ | :------- | :------ | | **formbricks-cloud** | ⬜️ Ignored ([Inspect](https://vercel.com/formbricks/formbricks-cloud/EtcukYvq63FLZUUYCkyM2zya3k1h)) | [Visit Preview](https://formbricks-cloud-git-feature-fix-ee-check-beh-e776ce-formbricks.vercel.app) | | Jun 6, 2024 2:36pm | | **formbricks-docs** | ⬜️ Ignored ([Inspect](https://vercel.com/formbricks/formbricks-docs/CUsGg7KqMDi8zBnyaeUF5s8bMeKS)) | [Visit Preview](https://formbricks-docs-git-feature-fix-ee-check-behi-749407-formbricks.vercel.app) | | Jun 6, 2024 2:36pm |

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