[BUG] Build failing: Update requirements file to install dependencies

[jcockhren]

Describe the bug
Builds are failing with the following error from logs:

-----> Python app detected
-----> Using Python version specified in runtime.txt
-----> Installing python-3.8.9
-----> Installing pip 20.2.4, setuptools 47.1.1 and wheel 0.36.2
-----> Installing SQLite3
-----> Installing requirements with pip
       ERROR: Could not open requirements file: [Errno 2] No such file or directory: '/tmp/build_6a08c693/prod.txt'
 !     Push rejected, failed to compile Python app.
 !     Push failed

The build fails b/c the requirements.txt file on the main branch references a non-existent prod.txt file. Update the requirements.txt file to point to this one.

To Reproduce
Any push or merge into the main branch.