Bump voluptuous-serialize from 2.0.0 to 2.1.0 (#211)

Bumps [voluptuous-serialize](https://github.com/balloob/voluptuous-serialize) from 2.0.0 to 2.1.0.
- [Release notes](https://github.com/balloob/voluptuous-serialize/releases)
- [Commits](home-assistant-libs/voluptuous-serialize@2.0.0...2.1.0)

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

Author: dependabot[bot]

homeassistant_cli/package_constraints.txt

@@ -13,7 +13,7 @@ pyyaml>=4.2b1
 requests==2.20.1
 ruamel.yaml==0.15.78
 voluptuous==0.11.5
-voluptuous-serialize==2.0.0
+voluptuous-serialize==2.1.0
 
 # 2.8 breaks requests-mock
 idna==2.7