[BUG] requirements.txt incorrectly referenced in catnip example

[JESii]

Describe the bug
When running the command docker build -t jseidel/catnip . get the error

executor failed running [/bin/sh -c pip install --no-cache-dir -r requirements.txt]: exit code: 1

To Reproduce
Steps to reproduce the behavior:

1. Create the Dockerfile as instructed
2. run the command docker build -t jseidel/catnip .
3. See the error

Expected behavior
The build command should complete without error

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: mac 11.6.5
• Docker Version 20.10.11, build dea9396

Additional context
The Dockerfile instructions are incorrect.
This line:
RUN pip install --no-cache-dir -r requirements.txt
should be:
RUN pip install --no-cache-dir -r flask-app/requirements.txt
to correctly reference the requirements.txt file

[JESii]

Drat... in the wrong directory so no bug.