Add Wall of Browser Bugs entry for #21120

Refs https://bugs.chromium.org/p/chromium/issues/detail?id=510079
Closes #21120

[skip sauce]

docs/_data/browser-bugs.yml

@@ -278,6 +278,16 @@
   origin: >
     Bootstrap#15298
 
+-
+  browser: >
+    Chrome (Linux)
+  summary: >
+    `<select>`'s pop-up menu is blank on some systems.
+  upstream_bug: >
+    Chromium#510079
+  origin: >
+    Bootstrap#21120
+
 -
   browser: >
     Safari