Change interactiveBorder to fix popup preview (go-gitea#23169)

Close go-gitea#23073. 
Used the solution as reference to the reply:
go-gitea#23073 (comment)
Here made the change inside the `contextpopup.js` because this is where
the popup component is created and tippy configuration is given.

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

web_src/js/features/contextpopup.js

@@ -31,6 +31,7 @@ export default function initContextPopups() {
     createTippy(this, {
       content: el,
       interactive: true,
+      interactiveBorder: 5,
       onShow: () => {
         el.firstChild.dispatchEvent(new CustomEvent('us-load-context-popup', {detail: {owner, repo, index}}));
       }