linter 0.1.62

* new lint: `prefer_mixin`
* new lint: `avoid_implementing_value_types`

Change-Id: Iaba2d1dd50511db935cf050ba49e7d10746be8cb
Reviewed-on: https://dart-review.googlesource.com/74880
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Phil Quitslund <[email protected]>

Author: pq

DEPS

@@ -95,7 +95,7 @@ vars = {
   "intl_tag": "0.15.6",
   "jinja2_rev": "2222b31554f03e62600cd7e383376a7c187967a1",
   "json_rpc_2_tag": "2.0.9",
-  "linter_tag": "0.1.61",
+  "linter_tag": "0.1.62",
   "logging_tag": "0.11.3+2",
   "markdown_tag": "2.0.2",
   "matcher_tag": "0.12.3",