Update template based on observed IRL usage

[chmurph2]

Stakeholder Overview (learn more)

I'm recommending the following changes based on months of observing how these PR templates are typically used:

1. Renames the ticket section to be more generic. Some teams prefer to link to the more informative project pitch than a (typically) vague Monday item.
2. Makes the Risk Estimate description optional. Most are just leaving the "replace this with..." text as is.

Risk Estimate (learn more)

• ✅ Negligible risk!

What GIF Best Describes This Pull Request?

[astupka]

Looks good to me. Looks like this will handle the need to link project pitches too.