Remove E12* from list of deliberately ignored flake8 rules

I367064ecaa6d1fd9d918f7ce003303e2db660647  Added E12 to the
ignored on purpose list, which also makes no sense E12 was never meant
to be skipped all together (I was the one who added E12 to the flake8
ignore list (Ifc8924914b5a0d625bc8df6442ee85eb21459cde)

Then I4cf246e3ec932ba0d2391eb8bcb793b28b005b4c came along and updated
the list to break out the E12 ignored on purpose list.

Drop all E12 rules from the ignored on purpose list, as we do not want
to ignore these on purpose.

Change-Id: Ic400047347a82aebbc0f6ce6f5061e7757a02d3d
Merge "Remove E12* from list of deliberately ignored flake8 rules"