[example] Use environment variable for example to run (#981)

[aHenryJard]

Proposed changes

• Lint an example file that is failing master build.
• Add an easy way to use another OpenCTI Url and token to run examples that the one used on CI

Related issues

• N/A

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

If this is a relatively large or complex change, kick off the discussion by explaining why you chose the solution you did and what alternatives you considered, etc...