Drop an old unnecessary workaround

This is another use of blacklist, but the entire workaround has
been obsolete since a day after it was added, per
https://pagure.io/fedora-infrastructure/issue/8096 . I double
checked and the mirror still exists and is still up to date.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

roles/copr/backend/files/provision/provision_builder_tasks.yml

@@ -135,13 +135,6 @@
     state: stopped
     enabled: no
 
-- name: blacklist ipv4 addresses for some mirrors
-  shell: ip route add unreachable "{{ item }}"
-  with_items:
-  - 204.157.3.70 # https://pagure.io/fedora-infrastructure/issue/8096
-  when:
-  - prepare_base_image is not defined
-
 - name: mount cache filesystem on /var/cache/mock
   mount: path=/var/cache/mock state=mounted src=mock_cache_tmpfs fstype=tmpfs opts="size=32G"
   when: mock_var_cache_tmpfs is defined