Add refactoring changelog label. Deprecate improvement

.cardano-dev.yaml

@@ -11,9 +11,12 @@ changelog:
       breaking: add
       compatible: add
       optimisation: add
-      improvement: add
       bugfix: add
+      refactoring: skip
       test: skip
       maintenance: skip
       release: skip
       documentation: skip
+
+      # deprecated, left here only for backwards compatible changelog generation
+      improvement: add

.github/PULL_REQUEST_TEMPLATE.md

@@ -9,7 +9,7 @@
   # - breaking       # the API has changed in a breaking way
   # - compatible     # the API has changed but is non-breaking
   # - optimisation   # measurable performance improvements
-  # - improvement    # QoL changes e.g. refactoring
+  # - refactoring    # QoL changes
   # - bugfix         # fixes a defect
   # - test           # fixes/modifies tests
   # - maintenance    # not directly related to the code
@@ -31,9 +31,9 @@ Highlight important bits of the PR that will make the review faster. If there ar
 - [ ] New tests are added if needed and existing tests are updated. See [Running tests](https://github.com/input-output-hk/cardano-node-wiki/wiki/Running-tests) for more details
 - [ ] Self-reviewed the diff
 
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