fix(memory): don't return Promise to debounce in ContactStore
fix(memory): don't return Promise to debounce in ContactStore

Prevents a memory leak where it holds onto a stale references of the
contactCache

nirmit/nylas-mail,nylas-mail-lives/nylas-mail,nirmit/nylas-mail,simonft/nylas-mail,nylas-mail-lives/nylas-mail,simonft/nylas-mail,simonft/nylas-mail,nylas/nylas-mail,nylas-mail-lives/nylas-mail,nirmit/nylas-mail,nylas/nylas-mail,nirmit/nylas-mail,simonft/nylas-mail,nylas/nylas-mail,simonft/nylas-mail,nylas/nylas-mail,nylas-mail-lives/nylas-mail,nirmit/nylas-mail,nylas/nylas-mail,nylas-mail-lives/nylas-mail