Fix spelling.

book/src/SUMMARY.md

@@ -29,7 +29,7 @@
     - [Map Building Test Harness](./chapter_24.md)
     - [BSP Room Dungeons](./chapter_25.md)
     - [BSP Interior Design](./chapter_26.md)
-    - [Cellular Automota Maps](./chapter_27.md)
+    - [Cellular Automata Maps](./chapter_27.md)
     - [Drunkard's Walk Maps](./chapter_28.md)
     - [Mazes and Labyrinths](./chapter_29.md)
     - [Diffusion-limited aggregation maps](./chapter_30.md)