Merge pull request Mbed-TLS#6082 from daverodgman/assemble-cl-case-backport2.28

Fix case of Mbed TLS in assemble_changelog.py - backport 2.28

Author: daverodgman

scripts/assemble_changelog.py

@@ -122,7 +122,7 @@ def format_category(cls, title, body):
 class TextChangelogFormat(ChangelogFormat):
     """The traditional Mbed TLS changelog format."""
 
-    _unreleased_version_text = '= mbed TLS x.x.x branch released xxxx-xx-xx'
+    _unreleased_version_text = '= Mbed TLS x.x.x branch released xxxx-xx-xx'
     @classmethod
     def is_released_version(cls, title):
         # Look for an incomplete release date