[doc] Re-enable nitpicky mode; Fix broken docs

2 jobs for nitpicky in 19 minutes and 40 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
failed #157885
docker-build
build_linux_36

00:19:40

73.0%
failed #157886
macosx
build_macosx_36

00:19:34

73.0%
 
Name Stage Failure
failed
build_macosx_36 Build
preparing documents... done
writing output... [ 20%] api
writing output... [ 40%] backend_api
writing output... [ 60%] develop
writing output... [ 80%] index
writing output... [100%] introduction

TESTS FAILED: beat.core-1.7.1b0-py36h1c6dc61_3.tar.bz2
ERROR: Job failed: exit status 1
failed
build_linux_36 Build
preparing documents... done
writing output... [ 20%] api
writing output... [ 40%] backend_api
writing output... [ 60%] develop
writing output... [ 80%] index
writing output... [100%] introduction

TESTS FAILED: beat.core-1.7.1b0-py36h1c6dc61_7.tar.bz2
ERROR: Job failed: exit status 1