infra: Fix SyntaxWarning in `chronos/manager.py`

[pitrou]

Running chronos/manager.py would emit a Python syntax warning as \$ is not a recognized escape sequence in Python:

/home/antoine/oss-fuzz/infra/experimental/chronos/manager.py:76: SyntaxWarning: invalid escape sequence '\$'
  ('"export PATH=/ccache/bin:\$PATH && python3.11 -m pip install -r /chronos/requirements.txt && '
/home/antoine/oss-fuzz/infra/experimental/chronos/manager.py:77: SyntaxWarning: invalid escape sequence '\$'
  'rm -rf /out/* && compile && cp -n /usr/local/bin/replay_build.sh \$SRC/"'

Make sure that Python does not try to unescape it, as it is intended as a shell escape sequence here.

[pitrou]

@DavidKorczynski

[DavidKorczynski]

let's land this one first https://github.com/google/oss-fuzz/pull/14313 as I assume some of this may be resolved in that PR