Remove obsolete pypi-mirror

We do not use pypi-mirror anymore, there's also no usage of pypimirror
in jeepyb. Remove the now obsolete module.

Related change: https://review.openstack.org/597370/
Change-Id: I13423bf55eac57da18449852e2102c9633d595bb

modules/openstack_project/files/pypi-mirror.yaml

@@ -1,15 +0,0 @@
-# This file is managed by puppet.
-# https://git.openstack.org/cgit/openstack-infra/system-config
-
-cache-root: /var/cache/pypimirror
-
-mirrors:
-  - name: openstack
-    projects:
-      - git://git.openstack.org/openstack/requirements
-    output: /var/lib/pypimirror/openstack
-
-  - name: openstack-infra
-    projects:
-      - git://git.openstack.org/openstack-infra/system-config
-    output: /var/lib/pypimirror/openstack-infra