Update "Searching GitLab like a pro" page

Why is this change being made?

This change is being made to make the "Searching GitLab like a pro" page more organised and concise, since before the content was a bit disorganised and repetitive. The content was also changed to be more browser and search engine agnostic.

How will this merge request impact page speed?

It should improve page speed since various images were removed from the page, so less images are loaded

Does this MR meet the acceptance criteria?

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