Upgrade requirements to singer-python 5.3.3 to support Windows

[rvm-xx]

Some issue with date format has been fixed in singer-python version 5.3.3 (reference below).
Current requirements are for singer-python=5.3.1.
Upgrading to singer-python 5.3.3 solves the error.

Thank you.

Reference
singer-io/singer-python@d50168c#diff-792e45ffe2c08b7e8eb8612296ca093e7f70b784176290e7fa3c54b0b6f62285