docs: invert grids index items overview

[MrBrunoWolff]

This only inverts the grid pro/entity manager texts, so they match the sidebar (Entity Manager first, Grid Pro second).

Before:

After:

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Do the changes you have made apply to both Current and Previous versions?
No

Have you done a trial build to check all new or changed links?
Yes

Is there anything else you would like us to know?
No