Change separator in phind conversation template from colon to newline

[dannydarvish]

Why are these changes needed?

From the documentation on HuggingFace, it can be seen that the Phind-CodeLlama models use newline separators in their conversation templates. As it is currently implemented, colon separators are used.

Related issue number (if applicable)

Checks

• [ ] I've run format.sh to lint the changes in this PR.
• [ ] I've included any doc changes needed.
• [ ] I've made sure the relevant tests are passing (if applicable).