YAML input select example missing spaces (#14356)

There are spaces missing in front of the potential values in the options list (all other lines have double space on indent). Not sure if it matters as my config file works without them, but since it's an example for brand new users, may want to fix.

source/_docs/configuration/yaml.markdown

@@ -45,10 +45,10 @@ input_select:
     name: Threat level
 # A collection is used for options
     options:
-     - 0
-     - 1
-     - 2
-     - 3
+      - 0
+      - 1
+      - 2
+      - 3
     initial: 0
 ```