Circle script: unset GOGC so it uses default

scripts/circle-test.sh

@@ -72,8 +72,7 @@ mv $GOPATH/bin/telegraf $CIRCLE_ARTIFACTS
 
 eval "git describe --exact-match HEAD"
 if [ $? -eq 0 ]; then
-    # Turn GOGC back on for making packages
-    export GOGC=100
+    unset GOGC
     tag=$(git describe --exact-match HEAD)
     echo $tag
     exit_if_fail ./scripts/build.py --package --version=$tag --platform=linux --arch=all --upload