Update examples.md

[arouinfar]

For #142

Examples.md should be updated for the 1.3 release.

• [x] Remove general examples covered in the PhET-iO Guide
• [x] Delete anything inaccurate
• [x] Ensure referenced phetioIDs still exist, update as necessary

[arouinfar]

Here's a snippet from the current examples:

Set the electronegativity with the sliders in the simulation or via the corresponding electronegativityProperty. To prevent users from changing the electronegativity, disable the slider using its enabledProperty. Alternatively, the Electronegativity Panel or slider may be completely hidden using the appropriate visibleProperty.

I'm not sure why I chose to call out the electronegativity slider. Hiding it (but not the panel) makes no sense.

[arouinfar]

Updated examples.md in the above commit, closing.