Fix ATTT&CK > ATT&CK in Usage.md

USAGE.md

@@ -542,7 +542,7 @@ from stix2 import Filter
 g0075 = src.query([ Filter("external_references.external_id", "=", "G0075") ])[0]
 ```
 
-Note: in prior versions of ATT&CK, mitigations had 1:1 relationships with techniques and shared their technique's ID. Therefore the above method does not work properly for techniques because technique ATTT&CK IDs are not truly unique. By specifying the STIX type you're looking for as `attack-pattern` you can avoid this issue.
+Note: in prior versions of ATT&CK, mitigations had 1:1 relationships with techniques and shared their technique's ID. Therefore the above method does not work properly for techniques because technique ATT&CK IDs are not truly unique. By specifying the STIX type you're looking for as `attack-pattern` you can avoid this issue.
 
 ```python
 from stix2 import Filter