PLT-3242 Fixed clicking on input labels on iOS (#3417)

* Prevented channel notification settings radiobuttons from multi-selecting

* Fixed clicking on input labels on iOS

webapp/sass/responsive/_mobile.scss

@@ -1051,3 +1051,9 @@
         }
     }
 }
+
+// on iOS, allow clicks within an input's label to actually propagate through to the input itself
+// http://stackoverflow.com/a/34810294/6325807
+label span {
+    pointer-events: none;
+}