[RFR] Fix Dead Link to Bulk Action Buttons in Docs

[bmuthoga]

Fixes #3355

What Does This PR Do?

This PR fixes the dead link to the Bulk Action Buttons implementation example in https://marmelab.com/react-admin/Actions.html#list-bulk-actions

"You can find a complete example of a custom Bulk Action button in the List documentation, 
in the Bulk Action Buttons section." <--- Here

Description Of Task To Be Completed

• Clicking on the link should navigate the user to the Bulk Action Buttons implementation example in List markdown instead of displaying a Not Found page

Any Background Context You Want To Provide?

• N/A

How can this be manually tested?

• Navigate to here
• Click on Bulk Action Buttons
• The page should navigate to here instead of displaying a Not Found page

References #3355

[djhi]

Thanks!

[WiXSL]

I just find out that every link in https://marmelab.com/react-admin/List.html pointing to MUI website is dead other than this.

[bmuthoga]

I can work on that too in a few hours time since it's related. Would you prefer it in a new branch or this same branch? Scratch that, I've seen there's one already 😄