fix(material/button-toggle): use smaller border radius (#31084)

Currently the button toggle uses the `corner-full` value for its broder radius which starts too look weird for a vertical group with text inside the toggles.

These changes switch to using the `corner-extra-large` value instead.

Fixes #31010.

(cherry picked from commit 90413f9)

Author: crisbeto

src/material/core/tokens/m3/mat/_standard-button-toggle.scss

@@ -14,7 +14,7 @@ $prefix: (mat, standard-button-toggle);
   $tokens: sass-utils.merge-all(
     token-definition.generate-typography-tokens($systems, label-text, label-large),
   (
-    shape: map.get($systems, md-sys-shape, corner-full),
+    shape: map.get($systems, md-sys-shape, corner-extra-large),
     hover-state-layer-opacity: map.get($systems, md-sys-state, hover-state-layer-opacity),
     focus-state-layer-opacity: map.get($systems, md-sys-state, focus-state-layer-opacity),
     text-color: map.get($systems, md-sys-color, on-surface),