style(listItem): removed unnecessary button background color and hover background color
style(listItem): removed unnecessary button background color and hover background color

fixes #2922. closes #5620.

ilovett/material,DevVersion/material,pwistbac/material,acoreyj/material,programmist/material,hodeyp/material,acoreyj/material,daniel-nagy/material,jadjoubran/material,hodeyp/material,imjoeco/material,clshortfuse/material,dmitriz/material,gkalpak/material,JonFerrera/material,colinskow/material,profoundry-us/material,kamilkisiela/material,BernhardRode/material,gmoothart/material,BernhardRode/material,imjoeco/material,gkalpak/material,Todd-Werelius/material,welkinhealth/material,robertmesserle/material,gmoothart/material,j3ski/material,isaaclyman/material,SamDLT/material,profoundry-us/material,JonFerrera/material,ErinCoughlan/material,welkinhealth/material,clshortfuse/material,david-gang/material,oostmeijer/material,ErinCoughlan/material,gkalpak/material,DerekLouie/material,bOOm-X/material,vertazzar/material,HarrisCorp/material,kamilkisiela/material,jadjoubran/material,SamDLT/material,ServiceManagementGroup/material,epelc/material,SamDLT/material,epelc/material,acoreyj/material,dmitriz/material,vertazzar/material,jelbourn/material,hodeyp/material,Splaktar/material,ServiceManagementGroup/material,robertmesserle/material,bOOm-X/material,programmist/material,imjoeco/material,welkinhealth/material,david-gang/material,miguelcobain/material,Splaktar/material,marekmicek/material,profoundry-us/material,BernhardRode/material,acoreyj/material,angular/material,hayloft/material,kwypchlo/material,2947721120/angular-material,jadjoubran/material,welkinhealth/material,Frank3K/material,CarmenPopoviciu/material,jadjoubran/material,2947721120/angular-material,marekmicek/material,robertmesserle/material,oostmeijer/material,vertazzar/material,daniel-nagy/material,CarmenPopoviciu/material,2947721120/angular-material,kwypchlo/material,Splaktar/material,DerekLouie/material,flowersinthesand/material,graingert/material,dmitriz/material,jelbourn/material,HipsterZipster/material,angular/material,gkalpak/material,HipsterZipster/material,Splaktar/material,kamilkisiela/material,marekmicek/material,ErinCoughlan/material,ServiceManagementGroup/material,flowersinthesand/material,hayloft/material,JonFerrera/material,pwistbac/material,DerekLouie/material,bluebirdtech/material,2947721120/angular-material,DevVersion/material,pwistbac/material,ilovett/material,colinskow/material,bOOm-X/material,HipsterZipster/material,isaaclyman/material,graingert/material,DevVersion/material,clshortfuse/material,miguelcobain/material,CarmenPopoviciu/material,gmoothart/material,CarmenPopoviciu/material,bluebirdtech/material,angular/material,graingert/material,epelc/material,bOOm-X/material,dmitriz/material,Todd-Werelius/material,programmist/material,programmist/material,flowersinthesand/material,jelbourn/material,flowersinthesand/material,kwypchlo/material,vertazzar/material,graingert/material,HipsterZipster/material,david-gang/material,HarrisCorp/material,gmoothart/material,j3ski/material,Frank3K/material,miguelcobain/material,DevVersion/material,robertmesserle/material,SamDLT/material,colinskow/material,imjoeco/material,profoundry-us/material,isaaclyman/material,bluebirdtech/material,HarrisCorp/material,crisbeto/material,pwistbac/material,Frank3K/material,Frank3K/material,crisbeto/material,JonFerrera/material,hodeyp/material,daniel-nagy/material,angular/material,colinskow/material,hayloft/material,oostmeijer/material,isaaclyman/material,Todd-Werelius/material,crisbeto/material,oostmeijer/material,miguelcobain/material,j3ski/material,ServiceManagementGroup/material,daniel-nagy/material,ilovett/material,epelc/material,jelbourn/material,HarrisCorp/material,david-gang/material,bluebirdtech/material,marekmicek/material,ilovett/material,kwypchlo/material,BernhardRode/material,kamilkisiela/material,DerekLouie/material,hayloft/material,ErinCoughlan/material,clshortfuse/material,j3ski/material,crisbeto/material,Todd-Werelius/material