fix(VExpansionPanels): outer panels styles cascade to inner panels (#9696)

fixes #9692

Author: jacekkarczmarczyk

packages/vuetify/src/components/VExpansionPanel/VExpansionPanel.sass

@@ -165,21 +165,21 @@
 
 // Modifier
 .v-expansion-panels--accordion
-  .v-expansion-panel
+  > .v-expansion-panel
     margin-top: 0
 
     &::after
       opacity: 1
 
 .v-expansion-panels--popout
-  .v-expansion-panel
+  > .v-expansion-panel
     max-width: $expansion-panel-popout-max-width
 
     &--active
       max-width: $expansion-panel-popout-active-max-width
 
 .v-expansion-panels--inset
-  .v-expansion-panel
+  > .v-expansion-panel
     max-width: $expansion-panel-inset-max-width
 
     &--active