Removed documentation about a module deleted from the repository

doc/import_doc/stiximport.json

@@ -1,8 +0,0 @@
-{
-  "description": "Module to import some stix stuff.",
-  "requirements": ["stix"],
-  "features": "The module imports MISP Attributes from a STIX 1 file, using the stix library, there is thus no special feature for users to make it work.",
-  "references": ["https://oasis-open.github.io/cti-documentation/", "https://github.com/STIXProject/python-stix"],
-  "input": "STIX format file",
-  "output": "MISP Event attributes"
-}