Support for using unicode characters in update_config()

[LeoHsiao1]

Hi!
Currently, update_config() converts the config to str type without encoding format.
So it does not support unicode characters. For example:

>>> jk.get_job('job1').update_config('中文') 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\Leo\AppData\Local\Programs\Python\Python39\lib\site-packages\jenkinsapi\job.py", line 640, in update_config
    response = self.jenkins.requester.post_url(url, params={}, data=config)
  ...
  File "C:\Users\Leo\AppData\Local\Programs\Python\Python39\lib\http\client.py", line 164, in _encode
    raise UnicodeEncodeError(
UnicodeEncodeError: 'latin-1' codec can't encode characters in position 0-1: Body ('中文') is not valid Latin-1. Use body.encode('utf-8') if you want to send it encoded in UTF-8.

So I submitted this PR to encode the config in utf-8 by default.
Looking forward to your review.

[LeoHsiao1]

There is another update_config() defined in view.py, I'm not sure what it's for.

jenkinsapi/jenkinsapi/view.py

Lines 184 to 194 in ec2a23f

	def update_config(self, config: str) -> str:
	"""
	Update the config.xml to the view
	"""
	url = self.get_config_xml_url()
	config = str(config) # cast unicode in case of Python 2
	response = self.get_jenkins_obj().requester.post_url(
	url, params={}, data=config
	)
	return response.text