Bump highlight.js from 9.17.1 to 10.4.1 in /book/8-begin

Bumps [highlight.js](https://github.com/highlightjs/highlight.js) from 9.17.1 to 10.4.1.
- [Release notes](https://github.com/highlightjs/highlight.js/releases)
- [Changelog](https://github.com/highlightjs/highlight.js/blob/master/CHANGES.md)
- [Commits](highlightjs/highlight.js@9.17.1...10.4.1)

Signed-off-by: dependabot[bot] <support@github.com>

book/8-begin/package.json

@@ -27,7 +27,7 @@
     "handlebars": "4.7.6",
     "he": "1.2.0",
     "helmet": "4.1.0-rc.2",
-    "highlight.js": "10.1.2",
+    "highlight.js": "10.4.1",
     "isomorphic-unfetch": "^3.0.0",
     "lodash": "4.17.20",
     "marked": "1.1.1",

book/8-begin/yarn.lock

@@ -4771,10 +4771,10 @@ helmet@4.1.0-rc.2:
   resolved "https://registry.yarnpkg.com/helmet/-/helmet-4.1.0-rc.2.tgz#12bc8f5c6f25350398fcefb0b522d048db60e934"
   integrity sha512-Ywt8Pfs54lvzguQ7JcSDo0+02VxMuDpkmPkt6nt08HHRA1h5UqSdvQquhEtotq9tQCx4icRSjSQpTIB9KU4PBA==
 
-highlight.js@10.1.2:
-  version "10.1.2"
-  resolved "https://registry.yarnpkg.com/highlight.js/-/highlight.js-10.1.2.tgz#c20db951ba1c22c055010648dfffd7b2a968e00c"
-  integrity sha512-Q39v/Mn5mfBlMff9r+zzA+gWxRsCRKwEMvYTiisLr/XUiFI/4puWt0Ojdko3R3JCNWGdOWaA5g/Yxqa23kC5AA==
+highlight.js@10.4.1:
+  version "10.4.1"
+  resolved "https://registry.yarnpkg.com/highlight.js/-/highlight.js-10.4.1.tgz#d48fbcf4a9971c4361b3f95f302747afe19dbad0"
+  integrity sha512-yR5lWvNz7c85OhVAEAeFhVCc/GV4C30Fjzc/rCP0aCWzc1UUOPUk55dK/qdwTZHBvMZo+eZ2jpk62ndX/xMFlg==
 
 hmac-drbg@^1.0.0:
   version "1.0.1"