Update package.json so @freecodecamp/curriculum in recent version 3.1.2 or later

[nathanhannig]

There is a bug fix to the challenge Create a Horizontal Line Using the hr Element that was released to master of "@freecodecamp/curriculum": "3.1.2"

The learn package.json is still referencing "@freecodecamp/curriculum": "3.1.1"

This means the bug fix will not make it to the freeCodeCamp website until the package.json of learn is updated. This is a bug that is causing a lot of confusion to users. People are posting duplicate reports of the issue on the forums, issue trackers, and guide.

freeCodeCamp/curriculum#247

https://github.com/freeCodeCamp/freeCodeCamp/issues?q=Create+a+Horizontal+Line+Using+the+hr+Element+is%3Aopen

https://github.com/freeCodeCamp/curriculum/issues?utf8=%E2%9C%93&q=is%3Aissue+is%3Aopen+Create+a+Horizontal+Line+Using+the+hr+Element+is%3Aopen+