clang release notes: document the -Wbool-operation improvement

Reviewed By: xbolva00

Differential Revision: https://reviews.llvm.org/D111215

Author: sylvestre

clang/docs/ReleaseNotes.rst

@@ -51,7 +51,7 @@ Major New Features
 Improvements to Clang's diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-- ...
+- -Wbitwise-instead-of-logical (part of -Wbool-operation) warns about use of bitwise with boolean operands which have side effects.
 
 Non-comprehensive list of changes in this release
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