Drop the lris2 submodule and stop CI depending on private instruments

[mikelangmayr]

• LRIS2 builds from its own repository with camerad as a dependency, so its sources no longer need to sit under camerad/Instruments; removes the submodule entry and its gitlink
• The docs and emulator workflows checked out submodules and built -DINSTRUMENT=hispec_tracking_camera, but that repository is private, so every run failed at checkout with "Repository not found". They now build the core with no instrument
• The instrument was incidental to what those jobs test: frame outputs, SHM and FITS writing, the Python module driving the emulator, and the install rules. None of it is instrument-specific, and instrument builds are covered by each instrument's own CI
• Drops the cryoscope emulator job
• Drops the nightly submodule update job, which failed every night on the same private repositories and has nothing left to bump
• cmake-workflow.yml is unchanged: it already checks out without submodules and only selects an instrument on manual dispatch, which is why it was the one job still passing