Rename the "Popular Topics" header to "Topics" inside the product solutions pages

[emilghittasv]

Description
As per the proposed figma specs, the "Popular Topics" header should be renamed to "Topics". While the header was successfully renamed inside the product landing pages (example: https://support.allizom.org/en-US/products/firefox) it still needs to be updated inside the product solutions pages (example:https://support.allizom.org/en-US/questions/new/firefox)

[akatsoulas]

PR mozilla/kitsune#6485

[emilghittasv]

I can confirm that this is verified fixed in stage.

Moving this ticket inside the release column.