deps: update acorn to 6.2.0

Includes support for bigint syntax so we can remove the acorn-bigint
plugin.

PR-URL: #28649
Reviewed-By: Ruben Bridgewater <[email protected]>
Reviewed-By: Richard Lau <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Yongsheng Zhang <[email protected]>

Author: targos

deps/acorn-plugins/acorn-bigint/CHANGELOG.md

@@ -1,3 +1,9 @@
+## 6.2.0 (2017-07-04)
+
+### New features
+
+Add support for `Import` nodes.
+
 ## 6.1.0 (2018-09-28)
 
 ### New features

deps/acorn-plugins/acorn-bigint/LICENSE

@@ -6,7 +6,7 @@ An abstract syntax tree walker for the
 ## Community
 
 Acorn is open source software released under an
-[MIT license](https://github.com/acornjs/acorn/blob/master/LICENSE).
+[MIT license](https://github.com/acornjs/acorn/blob/master/acorn-walk/LICENSE).
 
 You are welcome to
 [report bugs](https://github.com/acornjs/acorn/issues) or create pull