spec: filter Requires dependency for python(abi)

spec: filter Requires dependency for python(abi)

"AutoReq: no" disables all the Requires dependencies generation,
while they might be usable for building in some contexts.
This commit replaces it with the filter, which targets
only "python(abi) = 2.7" dependency. The issue with this dependency
is that there are two packages that provide it ("python" and
"python3-base"). It should be probably fixed in some other way,
but so far this way seems to be a workaround with the smallest
impact.

Change-Id: I163f22bddb8d1b65b91726e9a08439f1afc099c2