fix doxygen brief in subzero header files

src/IceTargetLoweringARM32.h

Index: src/IceTargetLoweringARM32.h
diff --git a/src/IceTargetLoweringARM32.h b/src/IceTargetLoweringARM32.h
index e3bebde0ed998e32a5e31493e231890117834827..41c9bf7b49deb190c4d9b00dd6e39e32fa23a0ff 100644
--- a/src/IceTargetLoweringARM32.h
+++ b/src/IceTargetLoweringARM32.h
@@ -8,7 +8,7 @@
 //===----------------------------------------------------------------------===//
 ///
 /// \file
-/// This file declares the TargetLoweringARM32 class, which implements the
+/// \brief Declares the TargetLoweringARM32 class, which implements the
 /// TargetLowering interface for the ARM 32-bit architecture.
 ///
 //===----------------------------------------------------------------------===//