; Revert "; Add a note about a bottleneck"

This reverts commit 9f9ce631.

It's still a bottleneck, but so are mapcar (with its effect on GC) and
concat. So our limits show in several places at once.
1 job for master in 10 seconds (queued for 1 second)
Status Job ID Name Coverage
failed #6556


Name Stage Failure
test-all Test
error: cannot lock ref 'refs/remotes/origin/master': Unable to create '/builds/emacs/emacs/.git/refs/remotes/origin/master.lock': File exists.

Another git process seems to be running in this repository, e.g.
an editor opened by 'git commit'. Please make sure all processes
are terminated then try again. If it still fails, a git process
may have crashed in this repository earlier:
remove the file manually to continue.
fatal: failed to run reflog
ERROR: Job failed: exit code 1