Changed emoji examples in indtroduction to be more differentiated.

Author: BethanyG

exercises/concept/cater-waiter/.docs/introduction.md

@@ -32,11 +32,11 @@ A `set` can be directly entered as a _set literal_ with curly `{}` brackets and
 Duplicates are silently omitted:
 
 ```python
->>> one_element = {'😀'}
-{'😀'}
+>>> one_element = {'➕'}
+{'➕'}
 
->>> multiple_elements = {'😀', '😃', '😄', '😁'}
-{'😀', '😃', '😄', '😁'}
+>>> multiple_elements = {'➕', '🔻', '🔹', '🔆'}
+{'➕', '🔻', '🔹', '🔆'}
 
 >>> multiple_duplicates =  {'Hello!', 'Hello!', 'Hello!', 
                             '¡Hola!','Привіт!', 'こんにちは！', 
@@ -91,19 +91,19 @@ Sets can hold different datatypes and _nested_ datatypes, but all `set` elements
 
 ```python
 # Attempting to use a list for a set member throws a TypeError
->>> lists_as_elements = {['😅','🤣'], 
-                        ['😂','🙂','🙃'], 
-                        ['😜', '🤪', '😝']}
+>>> lists_as_elements = {['🌈','💦'], 
+                        ['☁️','⭐️','🌍'], 
+                        ['⛵️', '🚲', '🚀']}
 
 Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
 TypeError: unhashable type: 'list'
 
 
 # Standard sets are mutable, so they cannot be hashed.
->>> sets_as_elements = {{'😅','🤣'}, 
-                        {'😂','🙂','🙃'}, 
-                        {'😜', '🤪', '😝'}}
+>>> sets_as_elements = {{'🌈','💦'}, 
+                        {'☁️','⭐️','🌍'}, 
+                        {'⛵️', '🚲', '🚀'}}
 
 Traceback (most recent call last):
   File "<stdin>", line 1, in <module>