Final call: fix object-has-alt example

Hey folks,
This pull request cleans up some minor issues with examples on the Object
has none-empty accessible name rule. This final call is open until October
16th. If you have any comments, please leave a review:

https://github.com/act-rules/act-rules.github.io/pull/1471

-- 
*Wilco Fiers*
Axe-core product owner - Co-facilitator WCAG-ACT - Chair ACT-R


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