Fix Pylint Error

Since this is an explicit error, I don't think there is any additional context
https://docs.python.org/3/library/exceptions.html

Author: askpatrickw

adafruit_minimqtt/matcher.py

@@ -55,7 +55,7 @@ def __getitem__(self, key):
                 raise KeyError(key)
             return node.content
         except KeyError:
-            raise from KeyError(key)
+            raise KeyError(key) from None
 
     def __delitem__(self, key):
         """Delete the value associated with some topic filter :key"""
@@ -67,7 +67,7 @@ def __delitem__(self, key):
                 lst.append((parent, k, node))
             node.content = None
         except KeyError:
-            raise from KeyError(key)
+            raise KeyError(key) from None
         else:  # cleanup
             for parent, k, node in reversed(lst):
                 if node.children or node.content is not None: