json_pointer.hpp: Mention more exception in documentation

Forgotten in dcd3a6c6 (move the catch of std::invalid_argument into
array_index(), 2020-03-23).

include/nlohmann/detail/json_pointer.hpp

@@ -325,6 +325,8 @@ class json_pointer
 
     @return integer representation of @a s
 
+    @throw parse_error.106  if an array index begins with '0'
+    @throw parse_error.109  if an array index begins not with a digit
     @throw out_of_range.404 if string @a s could not be converted to an integer
     */
     static int array_index(const std::string& s)

single_include/nlohmann/json.hpp

@@ -11357,6 +11357,8 @@ class json_pointer
 
     @return integer representation of @a s
 
+    @throw parse_error.106  if an array index begins with '0'
+    @throw parse_error.109  if an array index begins not with a digit
     @throw out_of_range.404 if string @a s could not be converted to an integer
     */
     static int array_index(const std::string& s)