Update dependency @gitlab/ui to v15

package.json

@@ -41,7 +41,7 @@
     "@babel/preset-env": "^7.8.4",
     "@gitlab/at.js": "1.5.5",
     "@gitlab/svgs": "1.130.0",
-    "@gitlab/ui": "14.17.0",
+    "@gitlab/ui": "15.5.0",
     "@gitlab/visual-review-tools": "1.6.1",
     "@rails/actioncable": "^6.0.3",
     "@sentry/browser": "^5.10.2",

yarn.lock

@@ -787,10 +787,10 @@
   resolved "https://registry.yarnpkg.com/@gitlab/svgs/-/svgs-1.130.0.tgz#0c2f3cdc0a4b0f54c47b2861c8fa31b2a58c570a"
   integrity sha512-azJ1E9PBk6fGOaP6816BSr8oYrQu3m3BbYZwWOCUp8AfbZuf0ZOZVYmlR9i/eAOhoqqqmwF8hYCK2VjAklbpPA==
 
-"@gitlab/ui@14.17.0":
-  version "14.17.0"
-  resolved "https://registry.yarnpkg.com/@gitlab/ui/-/ui-14.17.0.tgz#668f08318e9ef4d36a05c1ec13d531a8e46983b4"
-  integrity sha512-p75/lFQ0w5Mlg0DMdF2g/LW8DTJoSua4Xoh9BQO80o+Kw3ALQFOvvZAx17AW/MbgRD775I7Yv3V84H+s/xUqwg==
+"@gitlab/ui@15.5.0":
+  version "15.5.0"
+  resolved "https://registry.yarnpkg.com/@gitlab/ui/-/ui-15.5.0.tgz#96b563875ab8f587ee0e55d16c14c98f1d698957"
+  integrity sha512-AmYPR5X2UtipfkrZd8e8VvOo26YKHfXT+2XRd+Hysjdg+DBaGcUDTbO67cMb9dKkFPSgPdN67SgV+C8CBuBONQ==
   dependencies:
     "@babel/standalone" "^7.0.0"
     "@gitlab/vue-toasted" "^1.3.0"