markdownlint: minor fixes

Refresh the markdownlint config from openbmc-build-scripts and make
fixes as recommended.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I754e9570c75538ee36c9e126bb24018c842c6b40
diff --git a/.markdownlint.yaml b/.markdownlint.yaml
index 15c9e81..bcc4833 100644
--- a/.markdownlint.yaml
+++ b/.markdownlint.yaml
@@ -1,3 +1,6 @@
 default: true
+MD013: false
 MD024:
     siblings_only: true
+MD033:
+    allowed_elements: ["br", "sub", "sup"]