fix(VTextarea): correct area scaling when grown vertically in flex

fixes #20861

Author: KaelWD

packages/vuetify/src/components/VInput/VInput.sass

@@ -33,7 +33,7 @@
   .v-input--horizontal
     grid-template-areas: "prepend control append" "a messages b"
     grid-template-columns: max-content minmax(0, 1fr) max-content
-    grid-template-rows: auto auto
+    grid-template-rows: 1fr auto
 
     .v-input__prepend
       margin-inline-end: $input-affix-margin-inside

packages/vuetify/src/components/VTextarea/VTextarea.sass

@@ -43,6 +43,7 @@
       opacity: 0
       flex: 1
       min-width: 0
+      height: 100%
       transition: .15s opacity settings.$standard-easing
 
       &:focus,