Bump reno requirement to latest version and set default_branch (#220) (#221)

When we created a stable branch for qiskit-optimization we encountered
a bug in reno that required a branch named master to exist for traversing
the git history. To workaround that issue we temporarily added back a
branch named master while we waited for the fix [1] to be included in a
release. A new reno release has been published [2] and we can rely on
that version and delete the idle master branch now. This commit makes
this change and switches to using reno>=3.4.0 and uses the new
default_branch configuration option added in 3.4.0 to fix the issue.

[1] https://opendev.org/openstack/reno/commit/ed6bbae82e01edf781534d9e9cce21e0c55a49a6
[2] https://pypi.org/project/reno/3.4.0/

(cherry picked from commit 4953e56)

Co-authored-by: Matthew Treinish <[email protected]>

Author: mergify[bot]

releasenotes/config.yaml

@@ -1,2 +1,3 @@
 ---
 encoding: utf8
+default_branch: main

requirements-dev.txt

@@ -5,7 +5,7 @@ pylint>=2.8.3
 pylatexenc>=1.4
 stestr>=2.0.0
 ddt>=1.2.0,!=1.4.0
-reno>=3.2.0
+reno>=3.4.0
 Sphinx>=1.8.3,!=3.1.0,<4
 sphinx-panels
 sphinx-gallery