Change scanner's complex test:
```diff
- *coffee:
+ *coffee :
amount: 4
- *cookies:
+ *cookies :
amount: 4
```
According to https://play.yaml.io/main/parser, this example was invalid
in the first place. Adding a space makes it so that the colon is not
part of the alias name.
Also fix colons not being able to be part of anchors.
