ensure-twine: remove readme_renderer

This dependency was added with
Iaf4da5aedaa3814b2ecebed4391da2324d3e388d to prevent a warning when
using "twine check" with text/markdown descriptions.

Per [1], this check doesn't really do anything and will never fail.

We are now having issues using this role with with Python 3.8 on the
executor as the md dependency pulls in cmarkgfm which has binary
dependencies but does not publish any wheels; meaning the executor
fails to install as it does not have a toolchain setup.  Unfortunately
upstream is not particularly active, so building good manylinux wheels
is not something we're going to be able to deal with in a timely
fashion.

Given that this is not a failure, and isn't really doing anything and
blocks Python 3.8, it seems our best course is to remove this
dependency.

[1] pypa/twine#421

Change-Id: Iac5c9f63d41375889e4fdad67b9a45a24a644341

roles/ensure-twine/tasks/main.yaml

@@ -14,7 +14,7 @@
 - name: Ensure twine is installed
   block:
     - name: Ensure twine is installed
-      command: "{{ twine_python }} -m pip install twine!=1.12.0 readme_renderer[md]!=23.0 requests-toolbelt!=0.9.0 --user"
+      command: "{{ twine_python }} -m pip install twine!=1.12.0 requests-toolbelt!=0.9.0 --user"
 
     - name: Set pypi_twine_executable
       set_fact: