Update `grunt-contrib-imagemin` to `0.9.2`
Update `grunt-contrib-imagemin` to `0.9.2`

BoykoAlex/spring-cloud-dataflow-ui,cppwfs/spring-cloud-dataflow-ui,ghillert/spring-cloud-dataflow-ui,BoykoAlex/spring-cloud-dataflow-ui,ghillert/spring-cloud-dataflow-ui,cppwfs/spring-cloud-dataflow-ui,spring-cloud/spring-cloud-dataflow-ui,ghillert/spring-cloud-dataflow-ui,BoykoAlex/spring-cloud-dataflow-ui,spring-cloud/spring-cloud-dataflow-ui,spring-cloud/spring-cloud-dataflow-ui,cppwfs/spring-cloud-dataflow-ui,BoykoAlex/spring-cloud-dataflow-ui,ghillert/spring-cloud-dataflow-ui,cppwfs/spring-cloud-dataflow-ui,spring-cloud/spring-cloud-dataflow-ui