remove redundant rules from .editorconfig

[coliff]

This removes the unnecessary:

[{.travis.yml,package.json}]
# The indent size used in the `package.json` file cannot be changed
# https://github.com/npm/npm/pull/3180#issuecomment-16336516
indent_size = 2
indent_style = space

The preceding rules state indent size of 2 and spaces anyway. (plus that linked GitHub issue regarding package.json has been fixed as of npm 5)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.