python3-pyyaml: upgrade 5.4.1 -> 6.0

python3-pyyaml: upgrade 5.4.1 -> 6.0

Now uses "vendored" distutils from setuptools by default
rather than from Python stdlib.

Changes
=======

* https://github.com/yaml/pyyaml/pull/327
  -- Change README format to Markdown
* https://github.com/yaml/pyyaml/pull/483
  -- Add a test for YAML 1.1 types
* https://github.com/yaml/pyyaml/pull/497
  -- fix float resolver to ignore `.` and `._`
* https://github.com/yaml/pyyaml/pull/550
  -- drop Python 2.7
* https://github.com/yaml/pyyaml/pull/553
  -- Fix spelling of “hexadecimal”
* https://github.com/yaml/pyyaml/pull/556
  -- fix representation of Enum subclasses
* https://github.com/yaml/pyyaml/pull/557
  -- fix libyaml extension compiler warnings
* https://github.com/yaml/pyyaml/pull/560
  -- fix ResourceWarning on leaked file descriptors
* https://github.com/yaml/pyyaml/pull/561
  -- always require `Loader` arg to `yaml.load()`
* https://github.com/yaml/pyyaml/pull/564
  -- remove remaining direct distutils usage

Signed-off-by: Tim Orling <timothy.t.orling@intel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>