[CGData] Fix -Wpessimizing-move in CodeGenDataReader.cpp (NFC)

/llvm-project/llvm/lib/CodeGenData/CodeGenDataReader.cpp:78:12:
error: moving a local object in a return statement prevents copy elision [-Werror,-Wpessimizing-move]
    return std::move(E);
           ^
/llvm-project/llvm/lib/CodeGenData/CodeGenDataReader.cpp:78:12: note: remove std::move call here
    return std::move(E);
           ^~~~~~~~~~ ~
1 error generated.

llvm/lib/CodeGenData/CodeGenDataReader.cpp

@@ -75,7 +75,7 @@ Error IndexedCodeGenDataReader::read() {
   auto *End =
       reinterpret_cast<const unsigned char *>(DataBuffer->getBufferEnd());
   if (auto E = IndexedCGData::Header::readFromBuffer(Start).moveInto(Header))
-    return std::move(E);
+    return E;
 
   if (hasOutlinedHashTree()) {
     const unsigned char *Ptr = Start + Header.OutlinedHashTreeOffset;