[clang] Remove unnecessary virtual inheritance in TargetInfo

Since the `TargetInfo` has no diamond-like inheritance diagram,
the `virtual` keyword is not necessary.

Differential Revision: https://reviews.llvm.org/D148961

clang/include/clang/Basic/TargetInfo.h

@@ -202,7 +202,7 @@ enum OpenCLTypeKind : uint8_t {
 
 /// Exposes information about the current target.
 ///
-class TargetInfo : public virtual TransferrableTargetInfo,
+class TargetInfo : public TransferrableTargetInfo,
                    public RefCountedBase<TargetInfo> {
   std::shared_ptr<TargetOptions> TargetOpts;
   llvm::Triple Triple;