Update schema version to 500 (#71)

### Briefly, what does this PR introduce?


### What kind of change does this PR introduce?
- [ ] Bug fix (issue #__)
- [x ] New feature (issue #__)
- [ ] Documentation update
- [ ] Other: __

### Please check if this PR fulfills the following:
- [ ] Tests for the changes have been added
- [ ] Documentation has been added / updated
- [ x] Changes have been communicated to collaborators

### Does this PR introduce breaking changes? What changes might users
need to make to their code?
N/A
### Does this PR change default behavior?
N/A

edm4eic.yaml

@@ -9,7 +9,7 @@
 ## If there are schema version changes that can be evolved, see the podio documentation
 ## for an example: https://github.com/hegner/podio/blob/master/tests/schema_evolution.yaml
 ##
-schema_version: 400
+schema_version: 500
 
 options :
   # should getters / setters be prefixed with get / set?