dnsdist: Fix the version of alabaster when building the doc

Fixes
```
The alabaster extension used by this project needs at least Sphinx v3.4; it therefore cannot be built with this version.
```

diff --git a/pdns/dnsdistdist/docs/requirements.txt b/pdns/dnsdistdist/docs/requirements.txt
index 3d0421982c6c5d806f9dd83ed7428a77c6ef53b6..1f54e8b366ce7af875b29f8b74779320d00a4d30 100644 (file)
--- a/pdns/dnsdistdist/docs/requirements.txt
+++ b/pdns/dnsdistdist/docs/requirements.txt
@@ -6,3 +6,4 @@ sphinxcontrib-httpdomain
 sphinxcontrib-fulltoc
 docutils!=0.15,<0.18
 jinja2<3.1.0
+alabaster==0.7.13