Fix formatting of release notes

Change-Id: Iddc0ac31aff06010c0c4017ff36737d52e90e2d6

releasenotes/notes/etcd-3.4-11528a31a53451f6.yaml

@@ -1,6 +1,6 @@
 ---
 upgrade:
   - |
-    `etcd` has been updated to `v3.4.27`. Operators should read
-    `the etcd upgrade documentation <https://etcd.io/docs/v3.4/upgrades/upgrade_3_4/>`__
+    ``etcd`` has been updated to ``v3.4.27``. Operators should read the
+    `etcd upgrade documentation <https://etcd.io/docs/v3.4/upgrades/upgrade_3_4/>`__
     for upgrade notes.

releasenotes/notes/feature_neutron_install_tap-as-a-service-bdf99544a319ce7b.yaml

@@ -1,7 +1,6 @@
 ---
-
 features:
   - |
-    Adds the installation of the Neutron plugin `tap-as-a-service` in the
-    `neutron-base` image as a python package. This allows a user to configure
+    Adds the installation of the Neutron plugin ``tap-as-a-service`` in the
+    ``neutron-base`` image as a python package. This allows a user to configure
     this plugin and provide Neutron with port mirroring capabilities.

releasenotes/notes/fix-grafana-opensearch-datasource-96dc8061d9721af3.yaml

@@ -1,5 +1,5 @@
 ---
 fixes:
   - |
-    Adds missing `grafana-opensearch-datasource` plugin to the list of plugins
+    Adds missing ``grafana-opensearch-datasource`` plugin to the list of plugins
     in the docker image.

releasenotes/notes/overriding-global-upper-constraint-ca48a759c8f8d7b9.yaml

@@ -1,6 +1,6 @@
 ---
 features:
   - |
-     Introduces block `openstack_base_override_upper_constraints` to
+     Introduces block ``openstack_base_override_upper_constraints`` to
      provide users with the capability to globally override version
      constraints for services.

releasenotes/notes/update-prometheus-services-e53dfdb490ac700e.yaml

@@ -2,6 +2,7 @@
 upgrade:
   - |
     Update Prometheus services to latest releases:
+
     * blackbox_exporter 0.22.0 -> 0.24.0
     * elasticsearch_exporter 1.5.0 -> 1.6.0
     * haproxy_exporter 0.13.0 -> 0.15.0