job manager: encoding issue

[soxofaan]

reported by @mbuchhorn:

I get an error in the JobManager during the metadata write out to disk. It looks like due to unicode issues: UnicodeEncodeError: 'charmap' codec can't encode character '\u03c3' in position 56: character maps to

comes from

openeo-python-client/openeo/extra/job_management.py

Lines 599 to 600 in 74b716e

	with open(metadata_path, "w") as f:
	json.dump(job_metadata, f, ensure_ascii=False)

adding encoding='utf8' to the open() call fixes the problem. (I'm also not sure about that ensure_ascii=False)