Class name "URLPropertyScheam" is misspelled

**Describe the bug**
The name of the class `URLPropertyScheam` has two issues:
1) "Schema" is misspelled.
2) The capitalization of "URL" is inconsistent with other classes (eg. `UrlPropertyValue` or `UrlProperty`).

**Expected behavior**
The name of the class `URLPropertyScheam` is correctly spelled and is capitalized consistently with other classes.