Only do alphas after planned prereleases of ansible-core. (#404)

We can still do more releases if necessary.

docs/docsite/rst/roadmap/COLLECTIONS_9.rst

@@ -22,9 +22,9 @@ Release schedule
 
 :2023-09-18: ansible-core feature freeze, stable-2.16 branch created.
 :2023-09-25: Start of ansible-core 2.16 betas
-:2023-09-26: Ansible-9.0.0 alpha1 (roughly (bi-)weekly ``ansible`` alphas timed to coincide with ``ansible-core-2.16`` pre-releases).
+:2023-09-26: Ansible-9.0.0 alpha1
 :2023-10-16: First ansible-core 2.16 release candidate.
-:2023-10-24/31: Another Ansible-9.0.0 alpha release.
+:2023-10-17: Ansible-9.0.0 alpha2
 :2023-11-06: Ansible-core-2.16.0 released.
 :2023-11-06: Last day for collections to make backwards incompatible releases that will be accepted into Ansible-9. This includes adding new collections to Ansible 9.0.0; from now on new collections have to wait for 9.1.0 or later.
 :2023-11-07: Ansible-9.0.0 beta1 -- feature freeze [1]_ (weekly beta releases; collection owners and interested users should test for bugs).