Document change in the release notes

Author: FabianWolff

clang-tools-extra/docs/ReleaseNotes.rst

@@ -114,6 +114,9 @@ Improvements to clang-tidy
 - Fixed bug in :program:`run_clang_tidy.py` where the program would not
   correctly display the checks enabled by the top-level `.clang-tidy` file.
 
+- Fixed some false positives in the ``readability-redundant-smartptr-get``
+  check involving smart pointers to arrays.
+
 New checks
 ^^^^^^^^^^