nf-core subworkflows lint issue with no emit statements

Description of the bug

cf discussion in https://nfcore.slack.com/archives/CE6PELWR4/p1705575911588159

When a subworkflow has no emit statement, the linting is failing:

╭─ [✗] 1 Subworkflow Test Failed ──────────────────────────────────────────────╮
│                          ╷                        ╷                          │
│ Subworkflow name         │ File path              │ Test message             │
│╶─────────────────────────┼────────────────────────┼─────────────────────────╴│
│ utils_nextflow_pipeline  │ subworkflows/nf-core/… │ No workflow 'emit' block │
│                          │                        │ found                    │
│                          ╵                        ╵                          │
╰──────────────────────────────────────────────────────────────────────────────╯

That being said, this should be the exception rather than the rule, but there should be ways to deal with that properly

Command used and terminal output

No response

System information

No response

Start by locating the Python linting check that emits the “No workflow 'emit' block found” message for nf-core subworkflows, then reproduce the failure with a subworkflow that has no emit statement. Done means valid no-emit subworkflows are handled without a false lint failure while the usual emit validation remains intact.