mkdocs: pin dependencies

hack/docs.Dockerfile

@@ -6,12 +6,12 @@ FROM squidfunk/mkdocs-material:${MKDOCS_VERSION} AS base
 RUN apk add --no-cache git git-fast-import openssl \
   && apk add --no-cache --virtual .build gcc musl-dev \
   && pip install --no-cache-dir \
-    'lunr' \
-    'markdown-include' \
-    'mkdocs-awesome-pages-plugin' \
-    'mkdocs-exclude' \
-    'mkdocs-git-revision-date-localized-plugin' \
-    'mkdocs-macros-plugin' \
+    'lunr==0.7.0' \
+    'markdown-include==0.8.1' \
+    'mkdocs-awesome-pages-plugin==2.9.3' \
+    'mkdocs-exclude==1.0.2' \
+    'mkdocs-git-revision-date-localized-plugin==1.3.0' \
+    'mkdocs-macros-plugin==1.3.7' \
   && apk del .build gcc musl-dev \
   && rm -rf /tmp/*