feat: Support Dark mode for the widget (#4137)

Co-authored-by: Pranav Raj S <pranav@chatwoot.com>

app/javascript/widget/assets/scss/views/_conversation.scss

@@ -42,7 +42,6 @@
   }
 
   .agent-name {
-    color: $color-body;
     font-size: $font-size-small;
     font-weight: $font-weight-medium;
     margin: $space-small 0;
@@ -210,7 +209,6 @@
 
 .chat-bubble {
   @include light-shadow;
-  background: $color-woot;
   border-radius: $space-two;
   color: $color-white;
   display: inline-block;
@@ -242,7 +240,6 @@
   }
 
   &.agent {
-    background: $color-white;
     border-bottom-left-radius: $space-smaller;
     color: $color-body;