lldb: Migrate to MemoryBufferRef for createFileID (after 51d1d585)

I missed these two lldb users before deleting the `UnownedTag` API for
`createFileID` in 51d1d585. This should
fix the build.

lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp

@@ -221,7 +221,7 @@ TokenVerifier::TokenVerifier(std::string body) {
   clang::SourceManager SM(diags, file_mgr);
   auto buf = llvm::MemoryBuffer::getMemBuffer(body);
 
-  FileID FID = SM.createFileID(clang::SourceManager::Unowned, buf.get());
+  FileID FID = SM.createFileID(buf->getMemBufferRef());
 
   // Let's just enable the latest ObjC and C++ which should get most tokens
   // right.

lldb/source/Plugins/Language/ClangCommon/ClangHighlighter.cpp

@@ -168,7 +168,7 @@ void ClangHighlighter::Highlight(const HighlightStyle &options,
   clang::SourceManager SM(diags, file_mgr);
   auto buf = llvm::MemoryBuffer::getMemBuffer(full_source);
 
-  FileID FID = SM.createFileID(clang::SourceManager::Unowned, buf.get());
+  FileID FID = SM.createFileID(buf->getMemBufferRef());
 
   // Let's just enable the latest ObjC and C++ which should get most tokens
   // right.