Removing LLVM_EXPLICIT, as MSVC 2012 was the last reason for requiring the macro. NFC; LLVM edition.

llvm-svn: 229335
diff --git a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
index 8ff9553..8488ec8 100644
--- a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
@@ -633,7 +633,7 @@
   LogicOp(unsigned regSize, unsigned immLSB, unsigned immSize)
     : RegSize(regSize), ImmLSB(immLSB), ImmSize(immSize) {}
 
-  LLVM_EXPLICIT operator bool() const { return RegSize; }
+  explicit operator bool() const { return RegSize; }
 
   unsigned RegSize, ImmLSB, ImmSize;
 };