update MR change proposal template

Why is this change being made?

In the current product handbook, the template for a proposal to make a change links to an Issue template that does not exist and in fact, change proposals are actually an MR template

Does this MR meet the acceptance criteria?

Yes

Assign to DRI

• Did you assign this change to the correct DRI of the page or information you are changing?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what