Update the yarn version in circle.yml. (#2723)
Update the yarn version in circle.yml. (#2723)

See https://github.com/devtools-html/debugger.html/issues/2702 - it was
out-of-date.
ruturajv/debugger.html,jasonLaster/debugger.html,jbhoosreddy/debugger.html,borian/debugger.html,clarkbw/debugger.html,devtools-html/debugger.html,jasonLaster/debugger.html,tommai78101/debugger.html,tommai78101/debugger.html,borian/debugger.html,bomsy/debugger.html,clarkbw/debugger.html,darkwing/debugger.html,amitzur/debugger.html,wldcordeiro/debugger.html,jbhoosreddy/debugger.html,jasonLaster/debugger.html,jbhoosreddy/debugger.html,borian/debugger.html,borian/debugger.html,devtools-html/debugger.html,bomsy/debugger.html,bomsy/debugger.html,darkwing/debugger.html,tommai78101/debugger.html,jbhoosreddy/debugger.html,wldcordeiro/debugger.html,amitzur/debugger.html,wldcordeiro/debugger.html,wldcordeiro/debugger.html,darkwing/debugger.html,devtools-html/debugger.html,borian/debugger.html,tommai78101/debugger.html,wldcordeiro/debugger.html,darkwing/debugger.html,jasonLaster/debugger.html,ruturajv/debugger.html,bomsy/debugger.html,jasonLaster/debugger.html,devtools-html/debugger.html,wldcordeiro/debugger.html,devtools-html/debugger.html,jasonLaster/debugger.html,jbhoosreddy/debugger.html,amitzur/debugger.html,amitzur/debugger.html,devtools-html/debugger.html,ruturajv/debugger.html,bomsy/debugger.html,ruturajv/debugger.html,ruturajv/debugger.html,devtools-html/debugger.html,jbhoosreddy/debugger.html,clarkbw/debugger.html,wldcordeiro/debugger.html,ruturajv/debugger.html,jasonLaster/debugger.html,clarkbw/debugger.html,amitzur/debugger.html,darkwing/debugger.html,darkwing/debugger.html,tommai78101/debugger.html,clarkbw/debugger.html,borian/debugger.html,jbhoosreddy/debugger.html,bomsy/debugger.html,amitzur/debugger.html,darkwing/debugger.html,ruturajv/debugger.html,bomsy/debugger.html