Update requirements.txt (#295)

Author: himynamesdave

requirements.txt

@@ -537,7 +537,7 @@ stix2-patterns==2.0.0
     #   stix2-validator
 stix2-validator==3.2.0
     # via txt2stix
-stix2arango==1.1.6
+stix2arango==1.1.8
     # via
     #   -r requirements.in
     #   dogesec-commons