fix(VSelects/VCombobox/VAutocomplete): use rounding from Sass variable

fixes #21956

Author: J-Sek

packages/vuetify/src/components/VAutocomplete/VAutocomplete.sass

@@ -41,9 +41,10 @@
   .v-autocomplete
     &__content
       overflow: hidden
-
       @include tools.elevation($autocomplete-content-elevation)
-      @include tools.rounded($autocomplete-content-border-radius)
+
+      @at-root #{selector.append('.v-menu > .v-overlay__content', &)}
+        @include tools.rounded($autocomplete-content-border-radius)
 
     &__mask
       background: rgb(var(--v-theme-surface-light))

packages/vuetify/src/components/VCombobox/VCombobox.sass

@@ -41,9 +41,10 @@
   .v-combobox
     &__content
       overflow: hidden
-
       @include tools.elevation($combobox-content-elevation)
-      @include tools.rounded($combobox-content-border-radius)
+
+      @at-root #{selector.append('.v-menu > .v-overlay__content', &)}
+        @include tools.rounded($combobox-content-border-radius)
 
     &__mask
       background: rgb(var(--v-theme-surface-light))

packages/vuetify/src/components/VSelect/VSelect.sass

@@ -42,9 +42,10 @@
 
     &__content
       overflow: hidden
-
       @include tools.elevation($select-content-elevation)
-      @include tools.rounded($select-content-border-radius)
+
+      @at-root #{selector.append('.v-menu > .v-overlay__content', &)}
+        @include tools.rounded($select-content-border-radius)
 
     &__selection
       display: inline-flex