Minor documentation updates

[liquidz00]

Changes the following:

• Fixes a typo in contributors/index.rst (.vent) → (.venv)
• Changes code block directive to use console instead of shell. This was for syntax highlighting purposes, and to remain consistent throughout the documentation as this was the only instance of a shell code block.
• Adds a note to user guide about omitting URL scheme when instantiating a JamfClient object. SDK automatically handles this, if users add this information, the following error would be thrown:

requests.exceptions.ConnectionError: HTTPSConnectionPool(host='https', port=443): Max retries exceeded with url: /<sanitized>:443/api/v1/auth/token (Caused by NameResolutionError("<urllib3.connection.HTTPSConnection object at 0x104572ec0>: Failed to resolve 'https' ([Errno 8] nodename nor servname provided, or not known)"))