fix: REST API utf-8 decoding on creates/updates
fix: REST API utf-8 decoding on creates/updates

Creating or updating a document via the REST API would generate an error of:

`TypeError: the JSON object must be str, not 'bytes'`

Because get_data() returns bytes which must be explicitly converted to a string before parsing as JSON.

Defect introduced by efe94886a and a71a92341e
vjFaLk/frappe,vjFaLk/frappe,vjFaLk/frappe,vjFaLk/frappe