Replace static fixture for right_sidebar_spec

What does this MR do?

Replace right_sidebar.html.haml for right_sidebar_spec.js by already existing dynamically generated fixture.

What are the relevant issue numbers?

#24753 (closed)

app/assets/javascripts/boards/components/board_card.js.es6

@@ -54,6 +54,9 @@
       mouseDown () {
         this.showDetail = true;
       },
+      mouseMove() {
+        this.showDetail = false;
+      },
       showIssue (e) {
         const targetTagName = e.target.tagName.toLowerCase();