setup.py: roll back sleekxmpp requirement

to match what we have for lscsoft@sl7
17 jobs for setup.py-cleanup in 4 minutes and 23 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Dist
failed #698364
dist:tarball

00:04:23

failed #698341
dist:tarball

00:01:09

 
  Build
skipped #698344
build:debian:buster
skipped #698343
build:debian:stretch
skipped #698342
build:el7
 
  Test
skipped #698356
doc
skipped #698345
test:2.7
skipped #698346
test:3.5
skipped #698347
test:3.6
skipped #698348
test:3.7
skipped #698349
test:3.8
skipped #698354
test:buster:2.7
skipped #698355
test:buster:3.7
skipped #698350
test:el7:2.7
skipped #698351
test:el7:3.6
skipped #698352
test:stretch:2.7
skipped #698353
test:stretch:3.5
 
Name Stage Failure
failed
dist:tarball Dist
dist: found 3 matching files                       
.version: found 1 matching files

ERROR: Uploading artifacts to coordinator... error error=couldn't execute POST against https://git.ligo.org/api/v4/jobs/698364/artifacts?artifact_format=zip&artifact_type=archive: Post https://git.ligo.org/api/v4/jobs/698364/artifacts?artifact_format=zip&artifact_type=archive: net/http: TLS handshake timeout id=698364 token=DXZBJLXw
WARNING: Retrying... error=invalid argument
ERROR: Uploading artifacts to coordinator... error error=couldn't execute POST against https://git.ligo.org/api/v4/jobs/698364/artifacts?artifact_format=zip&artifact_type=archive: Post https://git.ligo.org/api/v4/jobs/698364/artifacts?artifact_format=zip&artifact_type=archive: net/http: TLS handshake timeout id=698364 token=DXZBJLXw
WARNING: Retrying... error=invalid argument
ERROR: Uploading artifacts to coordinator... error error=couldn't execute POST against https://git.ligo.org/api/v4/jobs/698364/artifacts?artifact_format=zip&artifact_type=archive: Post https://git.ligo.org/api/v4/jobs/698364/artifacts?artifact_format=zip&artifact_type=archive: net/http: TLS handshake timeout id=698364 token=DXZBJLXw
FATAL: invalid argument
ERROR: Job failed: exit code 1