reduce to 1 job per pipeline

1 job for master in 1 minute and 59 seconds (queued for 1 second)
Status Name Job ID Coverage
failed #46025


Name Stage Failure
failed Build
[] no changes from git+
[] no changes from git+
[] synchronised from git+

The following dependencies couldn't be met:
- coq -> ocaml >= 4.05.0
base of this switch (use `--unlock-base' to force)

ERROR: Job failed: exit code 1