fix(Accordion): remove white background for Header and Footer

Adjusted the bottom border radius on the Accordion's SectionFooter to
match the curve defined by the outer border-radius and border width.

Reported on Slack.

packages/orbit-components/src/Accordion/AccordionSection/components/SectionFooter.tsx

@@ -8,7 +8,9 @@ interface Props extends Common.Globals {
 
 const AccordionSectionFooter = ({ children, dataTest }: Props) => (
   <div
-    className="p-600 bg-white-normal shadow-level2 sticky bottom-0 flex"
+    // the border-radius is calculated based on the border-radius and border-width of the AccordionSection component
+    // outer border-radius is 4px, border-width is 1px so inner border-radius is 4px - 1px = 3px
+    className="p-600 rounded-b-normal shadow-level2 sticky bottom-0 flex"
     data-test={dataTest && `${dataTest}Footer`}
   >
     {children}

packages/orbit-components/src/Accordion/AccordionSection/components/SectionHeader.tsx

@@ -21,10 +21,7 @@ const AccordionSectionHeader = ({
   dataTest,
 }: Props) => (
   <div
-    className={cx(
-      "p-600 bg-white-normal flex items-center",
-      expanded ? "min-h-[19px]" : "min-h-form-box-normal",
-    )}
+    className={cx("p-600 flex items-center", expanded ? "min-h-[19px]" : "min-h-form-box-normal")}
     data-test={dataTest && `${dataTest}Header`}
   >
     <div className="flex grow items-center">{children}</div>

packages/orbit-components/src/Accordion/AccordionSection/index.tsx

@@ -29,6 +29,7 @@ const AccordionSection = ({
 
   return (
     <div
+      // Note: update SectionFooter's border-radius in case border-width or border-radius of this component changes
       className="border-elevation-flat-border-color rounded-100 my-200 bg-elevation-flat relative w-full border border-solid"
       data-test={dataTest}
     >