docs: fix up for errorignore convert-error signal removal

The commit that added that was reverted. Need to remove this
from docs cache manually.

Part-of: <!1422>
29 jobs for master in 55 seconds (queued for 8 seconds)
Status Job ID Name Coverage
  Build Docker
passed #3518268
alpine amd64 manifest builder docker

00:00:21

passed #3518267
android docker

00:00:21

passed #3518266
cerbero fedora amd64 docker

00:00:31

passed #3518265
fedora amd64 docker

00:00:20

passed #3518269
gst-indent amd64 docker

00:00:31

 
  Preparation
passed #3518271
gst indent

00:00:23

manual #3518270
manual
manifest
 
  Build
created #3518280
gstreamer
build cerbero cross-android universal
created #3518284
gst-ios-13.2
build cerbero cross-ios universal
created #3518281
gstreamer
build cerbero cross win32
created #3518282
gstreamer
build cerbero cross win64
created #3518279
gstreamer
build cerbero fedora x86_64
created #3518283
gst-macos-10.15
build cerbero macos x86_64
created #3518275
build clang fedora x86_64
created #3518278
1809 windows docker allowed to fail manual
build msys2
created #3518272
build nodebug fedora x86_64
created #3518273
build static fedora x86_64
created #3518274
build static nodebug fedora x86_64
created #3518276
1809 windows docker
build vs2017 amd64
created #3518277
1809 windows docker
build vs2017 x86
 
  Test
created #3518285
gstreamer
check fedora
created #3518286
gstreamer
integration testsuites fedora 1/4
created #3518287
gstreamer
integration testsuites fedora 2/4
created #3518288
gstreamer
integration testsuites fedora 3/4
created #3518289
gstreamer
integration testsuites fedora 4/4
created #3518290
gstreamer
valgrind bad
 
  Integrate
created #3518291
cross-android universal examples
created #3518293
gst-ios-13.2
cross-ios universal examples
created #3518292
documentation