[util] Relax hugo version check

The current check mandates the version in the form
"v0.59.0-.../extended". A packaged installation can also have the
version "v0.59.0/extended". The "-" is not required.

Signed-off-by: Tobias Wölfel <tobias.woelfel@mailbox.org>
diff --git a/util/build_docs.py b/util/build_docs.py
index 07682fb..b14dae7 100755
--- a/util/build_docs.py
+++ b/util/build_docs.py
@@ -224,7 +224,7 @@
 
     # Hugo version string example:
     # Hugo Static Site Generator v0.59.0-1DD0C69C/extended linux/amd64 BuildDate: 2019-10-21T09:45:38Z
-    return bool(re.search("v\d+\.\d+\.\d+-.*/extended", process.stdout))
+    return bool(re.search("v\d+\.\d+\.\d+.*/extended", process.stdout))
 
 
 def install_hugo(install_dir):