Update deploy-book.yml

Try to avoid rebuilding every time translation files change.

.github/workflows/deploy-book.yml

@@ -6,6 +6,10 @@ on:
   push:
     branches:
     - main
+    # Don't rebuild if we just have changed translation files
+    paths-ignore:
+    - _build/gettext/**
+    - locale/**
   workflow_dispatch:
 
 # This job installs dependencies, builds the book, and pushes it to `gh-pages`