extras/in_parallel.sh: remove erroneous quotes
extras/in_parallel.sh: remove erroneous quotes

$COMMAND can contain "make RM="

This patch fixes a regression caused by
https://github.com/weaveworks/scope/pull/2068/files#diff-42138a4802cce915f347919ccd707876R28

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