Bump tzinfo from 1.2.5 to 1.2.10 in /book

Bumps [tzinfo](https://github.com/tzinfo/tzinfo) from 1.2.5 to 1.2.10.
- [Release notes](https://github.com/tzinfo/tzinfo/releases)
- [Changelog](https://github.com/tzinfo/tzinfo/blob/master/CHANGES.md)
- [Commits](https://github.com/tzinfo/tzinfo/compare/v1.2.5...v1.2.10)

---
updated-dependencies:
- dependency-name: tzinfo
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/book/Gemfile.lock b/book/Gemfile.lock
index 7bcd1e6..c5a6ffb 100644
--- a/book/Gemfile.lock
+++ b/book/Gemfile.lock
@@ -189,7 +189,7 @@
     thor (0.19.1)
     thread_safe (0.3.6)
     tilt (1.4.1)
-    tzinfo (1.2.5)
+    tzinfo (1.2.10)
       thread_safe (~> 0.1)
     uglifier (3.2.0)
       execjs (>= 0.3.0, < 3)