DfciPkg/DfciTests: fix refresh server pip failure (#236)

## Description

Adds a command line switch to a pip command in the dockerfile. This
allows the docker image creation process to pass.

`--break-system-packages` was introduced in pip 23.0.1.

- https://pip.pypa.io/en/stable/news/#v23-0-1

- [ ] Impacts functionality?
- [ ] Impacts security?
- [ ] Breaking change?
- [ ] Includes tests?
- [ ] Includes documentation?

## How This Was Tested

Built on Windows 10.

## Integration Instructions

N/A

Fixes #234

DfciPkg/UnitTests/DfciTests/RefreshServer/Dockerfile

@@ -25,7 +25,7 @@ RUN apt update \
   && apt install python3 -y \
   && apt install python3-pip -y \
   && rm -rf /var/lib/apt/lists/* \
-  && pip3 install cython cherrypy flask pyOpenSSL
+  && pip3 install --break-system-packages cython cherrypy flask pyOpenSSL
 
 COPY Src/ ${WEB_DIR}/
 WORKDIR ${WEB_DIR}