make landing page version agnostic

[alexakreizinger]

this PR makes the docs landing page version agnostic by removing version info from the page title and associated splash image.

the Fluent Bit technical writers are making this change for a couple reasons:

• version info is still accessible from the docs site's version drop-down, which is also visible at all times across all pages.
• this eliminates the need to update the page title and associated image with each version increment.