Fix pip install path in mmlu.ipynb (openai#121)

# Thank you for contributing an eval! ♥️

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the guidelines below will result in the PR being closed automatically__.
Note that even if the criteria are met, that does not guarantee the PR
will be merged nor GPT-4 access granted. 🚨

__PLEASE READ THIS__:

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right now, users do not have access, so you will not be able to tell if
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## Eval details 📑
The current pip command in `mmlu.ipynb` will raise an error as blow.
```shell
ERROR: file:https:///home/ubuntu/repo/evals/examples does not appear to be a Python project: neither 'setup.py' nor 'pyproject.toml' found.
```
This PR modifies the command to be consistent with `lafand-mt.ipynb`

examples/mmlu.ipynb

@@ -21,7 +21,7 @@
  "outputs": [],
  "source": [
  "# Install, and download MMLU if you haven't already\n",
- "%pip install -e .\n",
+ "%pip install -e ../.\n",
  "\n",
  "!curl -O https://people.eecs.berkeley.edu/~hendrycks/data.tar\n",
  "!tar -xf data.tar\n",