[MC] Remove duplicate Contents field from MCLEBFragment.

There's already a Contents field in the MCEncodedFragmentWithFixups
base class. The Contents field in MCLEBFragment is private and there
is no accessor for it. It is initialized in the constructor, but that
should probably initialize the base class version.

llvm/include/llvm/MC/MCFragment.h

@@ -435,13 +435,11 @@ class MCLEBFragment final : public MCEncodedFragmentWithFixups<10, 1> {
   /// The value this fragment should contain.
   const MCExpr *Value;
 
-  SmallString<8> Contents;
-
 public:
   MCLEBFragment(const MCExpr &Value, bool IsSigned, MCSection *Sec = nullptr)
       : MCEncodedFragmentWithFixups<10, 1>(FT_LEB, false, Sec),
         IsSigned(IsSigned), Value(&Value) {
-    Contents.push_back(0);
+    getContents().push_back(0);
   }
 
   const MCExpr &getValue() const { return *Value; }