fix(styles): resolve css validation errors

fixes #15320

Author: KaelWD

packages/vuetify/src/components/VBtn/VBtn.sass

@@ -162,7 +162,7 @@
   display: flex
   flex: 1 0 auto
   min-width: 100% !important
-  max-width: auto
+  max-width: none
 
 .v-btn--is-elevated
   +elevation(2)

packages/vuetify/src/components/VChip/VChip.sass

@@ -150,7 +150,7 @@
 
 .v-chip--pill
   .v-chip__filter
-    margin-right: $chip-pill-filter-margin
+    margin: $chip-pill-filter-margin
 
   .v-avatar
     height: $chip-pill-avatar-size !important

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

@@ -24,8 +24,8 @@
   &.v-expansion-panels--hover
     > .v-expansion-panel
       > .v-expansion-panel-header
-        &:hover
-          +states($material)
+        &:hover::before
+          opacity: map-deep-get($material, 'states', 'hover')
 
 // Block
 .v-expansion-panels

packages/vuetify/src/components/VSkeletonLoader/VSkeletonLoader.sass

@@ -209,7 +209,7 @@
     ~ .v-skeleton-loader__card-heading
       border-radius: 0
 
-    &::first-child, &::last-child
+    &:first-child, &:last-child
       border-radius: inherit
 
   &__list-item