small improvements on html-parser (#4932)
small improvements on html-parser (#4932)

* remove unnecessary code

* not need to capture group when decoding attribute value

* fix eslint

KingMario/vue,Kingwl/vue,KingMario/vue,xueyaodeai/vue,KingMario/vue,vuejs/vue,Jinjiang/vue,cnchanning/vue,vuejs/vue,cnchanning/vue,cnchanning/vue,xueyaodeai/vue,Kingwl/vue,Hanks10100/vue,vuejs/vue,Hanks10100/vue,xueyaodeai/vue,Kingwl/vue,Ddder-FE/vue,Ddder-FE/vue,optimizely/vue,Jinjiang/vue,Hanks10100/vue,Jinjiang/vue,lizhiyao/vue,lizhiyao/vue,KingMario/vue,Ddder-FE/vue,Jinjiang/vue,Kingwl/vue,lizhiyao/vue,xueyaodeai/vue,vuejs/vue,Hanks10100/vue,lizhiyao/vue,Ddder-FE/vue