[stable-2.18] ci: refresh docs build dependencies (#2907)

* Bump antsibull-docs to 2.20.0.

* ci: refresh docs build dependencies

---------

Co-authored-by: Felix Fontein <[email protected]>
Co-authored-by: Ansible Documentation Bot <147556122+ansible-documentation-bot[bot]@users.noreply.github.com>

Author: ansible-documentation-bot[bot]

tests/constraints.in

@@ -3,7 +3,7 @@
 # This constraint file also pins other versions for which there are known limitations.
 
 sphinx == 7.2.5
-antsibull-docs == 2.19.1  # currently approved version
+antsibull-docs == 2.20.0  # currently approved version
 
 rstcheck < 6  # rstcheck 6.x has problem with rstcheck.core triggered by include files w/ sphinx directives https://github.com/rstcheck/rstcheck-core/issues/3
 sphinx-rtd-theme>=2.0.0  # Fix 404 pages with new sphinx -- https://github.com/ansible/ansible-documentation/issues/678

tests/requirements.txt

@@ -30,7 +30,7 @@ antsibull-changelog==0.34.0
     # via antsibull-docs
 antsibull-core==3.4.0
     # via antsibull-docs
-antsibull-docs==2.19.1
+antsibull-docs==2.20.0
     # via
     #   -c tests/constraints.in
     #   -r tests/requirements.in
@@ -40,7 +40,7 @@ antsibull-docutils==1.3.0
     # via
     #   antsibull-changelog
     #   antsibull-docs
-antsibull-fileutils==1.3.0
+antsibull-fileutils==1.4.0
     # via
     #   antsibull-changelog
     #   antsibull-core