Add Wall of Browser Bugs entry for #12359 (#20445)

https://bugzilla.mozilla.org/show_bug.cgi?id=504622
Refs #12359

[skip sauce]

docs/_data/browser-bugs.yml

@@ -148,6 +148,16 @@
   origin: >
     Bootstrap#20161
 
+-
+  browser: >
+    Firefox
+  summary: >
+    `min-width: 0` has no effect on `<fieldset>`
+  upstream_bug: >
+    Mozilla#504622
+  origin: >
+    Bootstrap#12359
+
 -
   browser: >
     Firefox (Windows)