group-members-page: Replace toSorted() with shallow copy + sort()

I didn't realize that `toSorted` is a relatively new method that is
not supported in older browser versions.¹

Thanks to @tsibley for using an old version of FireFox and catching this.

¹ <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/toSorted#browser_compatibility>

static-site/src/sections/group-members-page.tsx

@@ -100,7 +100,7 @@ const MembersTableContainer = styled.div`
 `;
 
 const MembersTable = ({ members }: { members: GroupMember[]}) => {
-  const sortedMembers = members.toSorted((a, b) => a.username.localeCompare(b.username));
+  const sortedMembers = [...members].sort((a, b) => a.username.localeCompare(b.username));
   function prettifyRoles(memberRoles: string[]) {
     // Prettify the role names by making them singular and capitalized
     return memberRoles.map((roleName) => startCase(roleName.replace(/s$/, ''))).join(", ");