docs(error/ueoe): add another possible cause

Mention unescaped quotes as another possible cause for this error.

Closes angular#15313

Author: emedws

docs/content/error/$parse/ueoe.ngdoc

@@ -4,6 +4,9 @@
 @description
 
 Occurs when an expression is missing tokens at the end of the expression.
-For example, forgetting a closing bracket in an expression will trigger this error.
 
-To resolve, learn more about {@link guide/expression Angular expressions}, identify the error and fix the expression's syntax.
+For example, forgetting to close a bracket or failing to properly escape quotes in an expression
+will trigger this error.
+
+To resolve, learn more about {@link guide/expression Angular expressions}, identify the error and 
+fix the expression's syntax.