[Request]: Update Observability docs landing page

[dedemorton]

Description

We received some feedback during the main Elastic docs landing page review that we should take into consideration (from Steve Kearns):

"The font is huge? The What do you want to Observe - I would imagine that we want the first/default selection to be Logs, given our "land with logs" strategy. Maybe an intro video on the landing page that shows the power of collecting logs, and how much more we can do as you add more signals?"

After meeting with other obs writers, we have decided to:

• Consider making the font size for the description smaller. (This is the text that begins with "...Rely on the most widely deployed observability....")
• Make the Logs tab under "What do you want to observe?" selected by default.
• Do not add a video.

Resources

See #3399 for more context/discussion around this request.

Which documentation set does this change impact?

Stateful only

Feature differences

n/a

What release is this request related to?

N/A

Collaboration model

The documentation team

Point of contact.

Main contact: n/a

Stakeholders: n/a