add explicit box-sizing of content-box to spectrum menu checkmark to avoid clipping in envs that use external bootsrap css globals (#6470)

Co-authored-by: Yihui Liao <[email protected]>

Author: Morts-PS

packages/@adobe/spectrum-css-temp/components/menu/index.css

@@ -87,6 +87,7 @@ governing permissions and limitations under the License.
 .spectrum-Menu-checkmark {
   transform: scale(1);
   opacity: 1;
+  box-sizing: content-box;
   /*
     Renamed from padding-y to padding-height to fix docs issue where fallback var replaced this value
     (due to old spectrum-css postcss-custom-properties-custom-mapping plugin).