[Bug] categories in conference collection is getting duplicated over multiple runs.

[rajatkb]

Describe the bug
The categories field is getting populated with the same data repeatedly over multiple runs, in the conference collection.

To Reproduce
Steps to reproduce the behavior:

1. Run the Scrapper-Service using python app.py -l debug -ls console --test True
   2.. Close it using Ctrl-C and run it again.
2. Check conference categories data, you will see the conference data being repeated

Expected behaviour
There should be unique entries in the conference categories field.

Additional context
The bug is associated with insertion logic, need fix in that ASAP.

[vipul-aggarwal-099]

I am interested with the issue.