Added the Pascal's Triangle problem in Python 3

[Ojaswi2000]

IMPORTANT: Please do not create a Pull Request without an issue.

All Submissions:

• I have read the CONTRIBUTING document.
• My code is written in Python3 and is ending with .py
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• I have checked that my submission does pass the test on LeetCode.com
• Does your filename follow the naming Conventions?
• Have you linked your PR to an Issue?

Closing issues

Put closes #XXXX in your comment to auto-close the issue that your PR fixes (if such).

[vJechsmayr]

No Issue linked - Please consider Contribution Guidelines