fix: match etherscan link styling to other views (remove extra border/hover/padding)

The etherscanLinkHtml helper had added border, px-1, hover:bg-fg,
hover:text-bg, and cursor-pointer classes that no other view uses.
All other views (addressDetail, addressToken, confirmTx, send, receive,
home, txStatus) use only 'inline-flex items-center' on etherscan links.
Removed the extra classes for consistency.

src/popup/views/transactionDetail.js

@@ -40,7 +40,7 @@ function blockieHtml(address) {
 function etherscanLinkHtml(url) {
     return (
         `<a href="${url}" target="_blank" rel="noopener" ` +
-        `class="inline-flex items-center border border-border px-1 hover:bg-fg hover:text-bg cursor-pointer"` +
+        `class="inline-flex items-center"` +
         `>${EXT_ICON}</a>`
     );
 }