Bump babel-plugin-istanbul from 5.1.0 to 5.1.1

Bumps [babel-plugin-istanbul](https://github.com/istanbuljs/babel-plugin-istanbul) from 5.1.0 to 5.1.1.
- [Release notes](https://github.com/istanbuljs/babel-plugin-istanbul/releases)
- [Changelog](https://github.com/istanbuljs/babel-plugin-istanbul/blob/master/CHANGELOG.md)
- [Commits](https://github.com/istanbuljs/babel-plugin-istanbul/compare/v5.1.0...v5.1.1)
Signed-off-by: dependabot[bot] <support@dependabot.com>

yarn.lock

@@ -1401,9 +1401,9 @@ babel-plugin-check-es2015-constants@^6.22.0:
     babel-runtime "^6.22.0"
 
 babel-plugin-istanbul@^5.1.0:
-  version "5.1.0"
-  resolved "https://registry.yarnpkg.com/babel-plugin-istanbul/-/babel-plugin-istanbul-5.1.0.tgz#6892f529eff65a3e2d33d87dc5888ffa2ecd4a30"
-  integrity sha512-CLoXPRSUWiR8yao8bShqZUIC6qLfZVVY3X1wj+QPNXu0wfmrRRfarh1LYy+dYMVI+bDj0ghy3tuqFFRFZmL1Nw==
+  version "5.1.1"
+  resolved "https://registry.yarnpkg.com/babel-plugin-istanbul/-/babel-plugin-istanbul-5.1.1.tgz#7981590f1956d75d67630ba46f0c22493588c893"
+  integrity sha512-RNNVv2lsHAXJQsEJ5jonQwrJVWK8AcZpG1oxhnjCUaAjL7xahYLANhPUZbzEQHjKy1NMYUwn+0NPKQc8iSY4xQ==
   dependencies:
     find-up "^3.0.0"
     istanbul-lib-instrument "^3.0.0"