Small tweaks to the product designer responsibilities

Why is this change being made?

There are some redundant responsibilities (duplicated or non-applicable) for the product designer job family. Additionally, the social media efforts don't encompass giving talks/presentations, something that is comparable to writing articles or responding on Twitter.

• Remove redundant responsibilities
• Add giving talks to social media efforts
• Fix headings

Does this MR meet the acceptance criteria?

Conformity

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