Configure our publish branch with only the latest commit (DataDog#3734)

GH pages branch is getting super big, so we want to reduce it by creating an orphan branch

Author: nogates

.github/workflows/docs.yml

@@ -37,3 +37,5 @@ jobs:
           enable_jekyll: false
           # Only deploy if there were changes
           allow_empty_commit: false
+          # GH pages branch is getting super big, so we want to reduce it by creating an orphan branch
+          force_orphan: true