Bump lodash from 4.17.11 to 4.17.21 in /_examples/gitbook

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.11 to 4.17.21.
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](lodash/lodash@4.17.11...4.17.21)

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

Author: dependabot[bot]

_examples/gitbook/yarn.lock

@@ -2276,8 +2276,8 @@ lodash.uniq@^4.5.0:
   resolved "https://registry.yarnpkg.com/lodash.uniq/-/lodash.uniq-4.5.0.tgz#d0225373aeb652adc1bc82e4945339a842754773"
 
 lodash@^4.13.1, lodash@^4.17.10, lodash@^4.17.5, lodash@^4.3.0, lodash@^4.8.0:
-  version "4.17.11"
-  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.11.tgz#b39ea6229ef607ecd89e2c8df12536891cac9b8d"
+  version "4.17.21"
+  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.21.tgz#679591c564c3bffaae8454cf0b3df370c3d6911c"
 
 lowercase-keys@^1.0.0:
   version "1.0.1"