cleanup gitignore (#3869)
cleanup gitignore (#3869)


alileza/prometheus,kangwoo/prometheus,Gouthamve/prometheus,kangwoo/prometheus,Gouthamve/prometheus,amorken/prometheus,prometheus/prometheus,GoogleCloudPlatform/prometheus,keegancsmith/prometheus,kangwoo/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,Gouthamve/prometheus,keegancsmith/prometheus,prometheus/prometheus,prometheus/prometheus,alileza/prometheus,keegancsmith/prometheus,prometheus/prometheus,keegancsmith/prometheus,kangwoo/prometheus,alileza/prometheus,alileza/prometheus,amorken/prometheus,GoogleCloudPlatform/prometheus,prometheus/prometheus,amorken/prometheus,alileza/prometheus,amorken/prometheus,GoogleCloudPlatform/prometheus,Gouthamve/prometheus,GoogleCloudPlatform/prometheus