Modify Brainfuck Tests

[rzuckerm]

Congrats on taking the first step to contributing to the Sample Programs repository maintained by The Renegade Coder!
For simplicity, please make sure that your pull request includes one and only one contribution.

Please fill one of the sections below as applicable.
Please also add any other relevant information to the Notes section at the bottom.
You may delete or just ignore any other sections.
For more information please refer to our contributing documentation

I Am Modifying an Existing Code Snippet or Existing Tests

• I fixed Modify Brainfuck Testing #4591
• I did not include any extra folders/libraries
• I have read about modifying existing code snippets or tests in the contributing documentation
• I have explained why this modification is necessary either in the issue linked above or in the notes below
• I named the pull request using Modify {PROJECT} {tests} in {LANGUAGE} format

Other Notes

The current docker image (redraiment/brainfuck) has been pulled from Docker Hub. I created my own here. Interestingly enough, the official Ubuntu package is called beef.