Move 2.10.0rc1 release date a few days forward. (#71270)

At yesterday's meeting it was decided to have ansible-2.10.0 depend on
ansible-base-2.10.1 so that we can get several fixes for ansible-base's
routing (including adding the gluster.gluster collection).
ansible-base-2.10.1 will release on September 8th.  So we will plan on
releasing ansible-2.10.0rc1 on the 10th.

https://meetbot.fedoraproject.org/ansible-community/2020-08-12/ansible_community_meeting.2020-08-12-18.00.html

docs/docsite/rst/roadmap/COLLECTIONS_2_10.rst

@@ -22,7 +22,7 @@ Release Schedule
 - 2020-08-18: Ansible 2.10 beta freeze.
   - No new modules or major features will be added after this date. In practice this means we will freeze the semver collection versions to compatible release versions. For example, if the version of community.crypto on this date was community-crypto-1.1.0; ansible-2.10.0 could ship with community-crypto-1.1.1.  It would not ship with community-crypto-1.2.0.
 - 2020-09-01: ansible-2.10.0 beta1.
-- 2020-09-08: ansible-2.10 final freeze/rc1.
+- 2020-09-10: ansible-2.10 final freeze/rc1.
   - After this date only changes blocking a release are accepted.
   - Collections will only be updated to a new version if a blocker is approved.  Collection owners should discuss any blockers at a community IRC meeting (on 9-10 and 9-17) to decide whether to bump the version of the collection for a fix. See the `Community IRC meeting agenda <https://github.com/ansible/community/issues/539>`_.