Mill 0.12.0-RC2-17-07e173 is incorrectly counting/reporting the tasks

[lefou]

When running the following command in the Mill repository, the output contains incorrect ticker messages.

> mill -j 0 __.fix
...
[5937/242] integration.failure[missing-build-file].fix 
Rewriting and linting 1 Scala sources against 3 rules
Rewriting and linting 1 Scala sources against 3 rules
Rewriting and linting 1 Scala sources against 3 rules
#12 [info] done compiling
[5939/242] integration.failure[misnamed-root-module].fix 
Rewriting and linting 1 Scala sources against 3 rules
[5941/242] integration.failure[invalid-meta-module].fix 
Rewriting and linting 1 Scala sources against 3 rules
Rewriting and linting 1 Scala sources against 3 rules
Rewriting and linting 1 Scala sources against 3 rules
[5943/242] integration.failure[invalid-subfolder-root-module].fix 
...

[lihaoyi]

This is a consequence of #3265, where we split terminal commands out to run serially, and 242 is the number of terminal commands. Should be an easy fix

[lihaoyi]

Should be fixed as part of #3577