install-build-deps: fix syntax error

If you run this script on an unsupported platform, you get:

  are currently supported: command not found

BUG=

Review URL: https://codereview.chromium.org/1881043005

Cr-Commit-Position: refs/heads/master@{#387093}

build/install-build-deps.sh

@@ -76,7 +76,7 @@ ubuntu_codenames="(precise|trusty|utopic|vivid|wily)"
 if [ 0 -eq "${do_unsupported-0}" ] && [ 0 -eq "${do_quick_check-0}" ] ; then
   if [[ ! $lsb_release =~ $ubuntu_codenames ]]; then
     echo "ERROR: Only Ubuntu 12.04 (precise), 14.04 (trusty), " \
-      "14.10 (utopic), 15.04 (vivid) and 15.10 (wily) "
+      "14.10 (utopic), 15.04 (vivid) and 15.10 (wily) " \
       "are currently supported" >&2
     exit 1
   fi