Update content.json

Have updated CTAs for Sharing, Collaborating, Community, Privacy and Open Practices as per bug 1027264. Only part I wasn't sure about was the # of brackets on the bottom. Originally had 5, now has 4. Sorry if it's messy, this is my first pull request with Webmaker.
I'm just staring at these links and wondering if the better anchor tag placement would be

Use our templates to [make your own remixable teaching kits](#) and activities like these.

... but maybe that means I've just spent too much time with SEO jerks.