EditorConfig: Relax 2 space indentation rule to only the `package.json

[ntwb]

This is a partial revert of 7c9cfe4, originally it was added so that it was in sync with WordPress' .editorconfig, rather WordPress should follow suit of how it's done here.

Follow up to #1029 / #1022

[ntwb]

Upstream core ticket https://core.trac.wordpress.org/ticket/40946

[aduth]

Should we restore tabs to composer.json here as well?

Do .yml files need two-spaces generally, or is it just Travis being picky?

[nylen]

The composer.json default is 4 spaces (and composer.lock, which still uses 4 spaces in master), but it looks like composer is pretty good about preserving existing indentation.

[nylen]

http://www.yaml.org/faq.html

Why does YAML forbid tabs?

Tabs have been outlawed since they are treated differently by different editors and tools. And since indentation is so critical to proper interpretation of YAML, this issue is just too tricky to even attempt. Indeed Guido van Rossum of Python has acknowledged that allowing TABs in Python source is a headache for many people and that were he to design Python again, he would forbid them.

🍿 🍿 🍿

[ntwb]

I added commit 09b849b that switches composer.json to tabs 🤖

[coveralls]

Coverage remained the same at 17.816% when pulling 9c12e12 on ntwb:fix/editorconfig-json into c29f11f on WordPress:master.