Revert "widget/material: propagate ButtonLayout minimum constraints to content"

This reverts commit 52ccc183b5.

Reason for revert:

This doesn't seem like a good idea after all. The reason for the change was to
propagate the minimum constraints to the button content. But in the simplest case,
a label, stretching the button will make the label stretch as well, leaving the label
top-aligned.

We'll revisit this issue if a real use-case comes up.

widget/material/button.go

@@ -109,9 +109,9 @@ func (b ButtonLayout) Layout(gtx *layout.Context, button *widget.Button, w layou
 			}
 		}),
 		layout.Stacked(func() {
+			gtx.Constraints.Width.Min = hmin
+			gtx.Constraints.Height.Min = vmin
 			layout.Center.Layout(gtx, func() {
-				gtx.Constraints.Width.Min = hmin
-				gtx.Constraints.Height.Min = vmin
 				b.Inset.Layout(gtx, func() {
 					paint.ColorOp{Color: b.Color}.Add(gtx.Ops)
 					w()

widget/material/material_test.go

@@ -1,25 +0,0 @@
-// SPDX-License-Identifier: Unlicense OR MIT
-
-package material
-
-import (
-	"image"
-	"testing"
-
-	"gioui.org/layout"
-	"gioui.org/widget"
-)
-
-func TestButtonLayout(t *testing.T) {
-	var gtx layout.Context
-	gtx.Reset(nil, image.Point{X: 100, Y: 100})
-
-	ButtonLayout{}.Layout(&gtx, new(widget.Button), func() {
-		if got, exp := gtx.Constraints.Width.Min, 100; got != exp {
-			t.Errorf("minimum width is %d, expected %d", got, exp)
-		}
-		if got, exp := gtx.Constraints.Height.Min, 100; got != exp {
-			t.Errorf("minimum width is %d, expected %d", got, exp)
-		}
-	})
-}