[3.8] Fix documentation build by pinning Alabaster version to 0.7.13 (GH-113815) (#113899)

Alabaster is Sphinx's dependency. Alabaster 0.7.14 released on 2024-01-08 dropped support for Sphinx 3.3 and earlier.

(cherry picked from commit f86e20e)

https://alabaster.readthedocs.io/en/latest/changelog.html

Co-authored-by: Maciej Olko <[email protected]>

Author: miss-islington

Doc/requirements.txt

@@ -10,6 +10,8 @@ sphinx==2.4.4
 docutils==0.17.1
 # Jinja version is pinned to a version compatible with Sphinx version 2.4.4.
 jinja2==3.0.3
+# Alabaster version is pinned to a version compatible with Sphinx version 2.4.4.
+alabaster==0.7.13
 
 blurb