ci : enable main-cuda build (#3282)
This commit re-enables the main-cuda Docker build in the CI workflow.
The main-cuda Dockerfile has been updated to remove build artifacts
and also print the size of the /app directory after the build. A similar
change was recently made to the musa Dockerfile, and perhaps this job
was also having similar disk space issues.
The motivation for this change is that this configuration has been
disabled for a while due to persistent build failures. However, the
actual logs are now longer available.
Resolves: https://github.com/ggml-org/whisper.cpp/issues/3040
