Remove all traces of NUM_THREADS

The code that looked at CAIRO_TEST_NUM_THREADS was removed seven years
ago in commit 6ef9779a, because it was dead code. I have not
managed to figure out how long exactly this code was dead already.

This commit removes the last traces of NUM_THREADS.

Signed-off-by: Uli Schlachter <psychon@znc.in>
1 job for master in 5 minutes and 39 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #64545
fedora:test

00:05:39

 
Name Stage Failure
failed
fedora:test Test
make[1]: *** [Makefile:906: check-recursive] Error 1
make[1]: Leaving directory '/builds/cairo/cairo'
make: *** [Makefile:1358: check] Error 2
Uploading artifacts...
test/*.log: found 2 matching files
test/pdiff/*.log: found 1 matching files

test/output: found 2101 matching files

Uploading artifacts to coordinator... ok
id=64545 responseStatus=201 Created token=z_3WmWLi
ERROR: Job failed: exit code 1