Remove unused dependency not

Related-to GH-8.
Closes GH-9.

Reviewed-by: Titus Wormer <[email protected]>

Author: remcohaszing

package.json

@@ -47,7 +47,6 @@
     "hast-util-has-property": "^3.0.0",
     "hast-util-to-string": "^3.0.0",
     "hast-util-whitespace": "^3.0.0",
-    "not": "^0.1.0",
     "nth-check": "^2.0.0",
     "property-information": "^6.0.0",
     "space-separated-tokens": "^2.0.0",