examples: fully automated fixing of E30 pep8 errors

probably these simple newline fixes (pep8 E30x error classes - see https://pep8.readthedocs.org/en/latest/intro.html#error-codes) in all mpl examples are less controversial than my pep8 changes in #3425 and #3488.

For this PR I used my patched versions of pep8 and autopep8 - no manual adjustment was required - yeah :)