ensure grammar is aligned with string_serialization in yaml

The yaml has string serializations

```yaml
node rename:
is_a: node change
description: >-
A node change where the name (aka rdfs:label) of the node changes
slots:
- old value
- new value
- has textual diff
- new language
- old language

slot_usage:
old value:
multivalued: false
new value:
multivalued: false
change description:
string_serialization: "rename {about node} from {old value} to {new value}"
examples:
- value: "rename UBERON:0002398 from 'manus' to 'hand'"
description: "replacing the rdfs:label of 'manus' on an uberon class with the rdfs:label 'hand'"
```

but these are not always aligned with the grammar