Port #18111 to v4

Add http://wkbug.com/150715 to Wall of Browser Bugs

[skip sauce]
[skip validator]

docs/_data/browser-bugs.yml

@@ -289,3 +289,13 @@
     WebKit#146244, Safari#21509310
   origin: >
     Bootstrap#15968
+
+-
+  browser: >
+    Safari (iOS 9+)
+  summary: >
+    Sometimes excessive automatic zoom is applied after opening a modal, and the user isn't allowed to zoom out
+  upstream_bug: >
+    WebKit#150715
+  origin: >
+    WebKit#138201