remove mode_name from output path

[juliasloan25]

Currently, our output directory includes the mode_name, typically amip, slabplanet, or climaatmos, in the output directory. We should remove this, since the job ID is also in the output dir path and this contains the mode name already.

Links

• COUPLER_OUTPUT_DIR defined here
• benchmark artifact dirs defined here
• atmos output dir defined here

To Do

• change code in above locations
• update buildkite pipelines
• check buildkite outputs