Correctly remove resize event listener on terminal unmount
Correctly remove resize event listener on terminal unmount

Fixes console errors

paulbellamy/scope,kinvolk/scope,kinvolk/scope,alban/scope,alban/scope,weaveworks/scope,paulbellamy/scope,alban/scope,paulbellamy/scope,alban/scope,kinvolk/scope,weaveworks/scope,kinvolk/scope,weaveworks/scope,paulbellamy/scope,paulbellamy/scope,weaveworks/scope,alban/scope,weaveworks/scope,alban/scope,kinvolk/scope,paulbellamy/scope,kinvolk/scope,weaveworks/scope