fix: replace old-style <br> tags to fix Mermaid rendering issues (#13792)

web/app/components/base/mermaid/utils.spec.ts

@@ -0,0 +1,8 @@
+import { cleanUpSvgCode } from './utils'
+
+describe('cleanUpSvgCode', () => {
+  it('replaces old-style <br> tags with the new style', () => {
+    const result = cleanUpSvgCode('<br>test<br>')
+    expect(result).toEqual('<br/>test<br/>')
+  })
+})