Merge branch 'bschubert/1.91.1' into 'master'

NEWS: update release notes for version 1.91.1

See merge request BuildStream/buildstream!1646
diff --git a/NEWS b/NEWS
index 49d73c0..1c69548 100644
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,10 @@
 (unreleased)
 ============
 
+==================
+buildstream 1.91.1
+==================
+
 API
 ---
 
@@ -11,9 +15,13 @@
   o BREAKING CHANGE: 'Element.node_subst_list' has been removed. Please use
     'Element.node_subst_sequence_vars' instead.
 
+  o BREAKING CHANGE: Workspace incremental builds have been temporarily disabled
+
   o A new 'Node.strip_node_info()' is available and allows getting the
     underlying data structure for the given node.
 
+  o BuildStream now requires Buildbox-casd 0.0.3 at minimum
+
 ==================
 buildstream 1.91.0
 ==================