Remove example test from java_http

[alex-james-dev]

This is a PR for the java_http GSoC '23 project 🌞.
Relevant tracking issue: #957.

Purpose

The purpose of this PR is to remove the example test that was generated by the dart create command as requested in #980 (comment).

We plan to remove the other files generated by the dart create command that we don't need, see #982.

Reviewers

@natebosch

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