bump mdbook version to silence warning in CI

yaahc · yaahc · commit 7642673d5b43 · 2022-05-27T14:36:58.000-07:00
diff --git a/.env b/.env
@@ -1,4 +1,4 @@
-MDBOOK_VERSION=0.4.8
+MDBOOK_VERSION=0.4.18
 MDBOOK_LINKCHECK_VERSION=0.7.4
 MDBOOK_TOC_VERSION=0.6.3
 
