removing .yarnclean as its usage is not recommended

.yarnclean

-# test directories
-__tests__
-test
-tests
-powered-test
-
-# asset directories
-docs
-doc
-website
-images
-assets
-
-# examples
-example
-examples
-
-# code coverage directories
-coverage
-.nyc_output
-
-# build scripts
-Makefile
-Gulpfile.js
-Gruntfile.js
-
-# configs
-.tern-project
-.gitattributes
-.editorconfig
-.*ignore
-.eslintrc
-.jshintrc
-.flowconfig
-.documentup.json
-.yarn-metadata.json
-.*.yml
-*.yml
-
-# misc
-*.gz
-*.md
-
-!tslint/lib/test/*
-!istanbul/lib/assets/*
-!remap-istanbul/node_modules/istanbul/lib/assets/*