Build Tools: Update `grunt-sass` to `2.0.0`

[netweb]

Following on from bumping Node.js to 8.9.3 in [42461]/#35105 grunt-sass's node-sass 3.x version dependancy is not compatable with Node.js 8.x, as such grunt-sass needs to be bumped to the latest 2.0.0 release which includes node-sass 4.x, as such before Travis CI can be bumped to use Node.js 8.9.3 this grunt-change` update is required

• grunt-sass 2.0.0 release: ​https://github.com/sindresorhus/grunt-sass/releases/tag/v2.0.0
• grunt-sass diff of 1.2.1 -> 2.0.0 ​https://github.com/sindresorhus/grunt-sass/compare/v1.2.1...v2.0.0

Previously using Node.js 6.9.1 and grunt-sass 1.2.1:

├─┬ grunt-sass@1.2.1
│ ├── each-async@1.1.1
│ ├── node-sass@3.13.1
│ └── object-assign@4.1.1

Proposed in this ticket using Node.js 8.9.3 and grunt-sass 2.0.0

├─┬ grunt-sass@2.0.0
│ ├── each-async@1.1.1
│ ├── node-sass@4.7.2
│ └── object-assign@4.1.1

Travis CI test on my fork for the above change: ​https://travis-ci.org/ntwb/wordpress/jobs/329329116

Note: Travis CI is still using Node.js 6.9.1, after this ticket has been committed Travis CI will then be bumped to use Node.js 8.9.3 via 35105.4-travis.diff

[dd32]

In 42463:

Build: Bump grunt-sass to v2.0.0 from v1.2.1 for Node 8.x support.

Changes: ​https://github.com/sindresorhus/grunt-sass/compare/v1.2.1...v2.0.0

Props netweb.
See #35105.
Fixes #43097.

[dd32]

As expected, this didn't affect the built files:
​https://build.trac.wordpress.org/changeset/42292

[jorbin]

committed to 5.0 in [43684]