rpm.spec: bump python dependency to 2.6
We are about to drop 2.4 requirement in Mercurial's setup.py, we bump rpm
dependency first for the sake of smaller changeset. Clean up of the spec file
can come after the dependency is actually dropped.
$ rm -rf a
$ hg init a
$ cd a
$ echo a > a
$ hg ci -Am0
adding a
$ hg tag t1 # 1
$ hg tag --remove t1 # 2
$ hg co 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg tag -f -r0 t1
$ hg tags
tip 3:a49829c4fc11
t1 0:f7b1eb17ad24
$ cd ..