Upgrade Hugo

It is a good idea to stay up to date, anyway, but in this instance the
motivation is to get across the breaking changes in
https://github.com/gohugoio/hugo/releases/tag/v0.148.0 that affect how
layouts work (something that I am about to use when I introduce support
for Graphviz diagrams).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

hugo.yml

@@ -14,4 +14,4 @@ module:
   - source: content
     target: content
 params:
-  hugo_version: 0.145.0
+  hugo_version: 0.149.1