Bump index version to start storing RefKind::Call

Author: HighCommander4

clang-tools-extra/clangd/index/Serialization.cpp

@@ -457,7 +457,7 @@ readCompileCommand(Reader CmdReader, llvm::ArrayRef<llvm::StringRef> Strings) {
 // The current versioning scheme is simple - non-current versions are rejected.
 // If you make a breaking change, bump this version number to invalidate stored
 // data. Later we may want to support some backward compatibility.
-constexpr static uint32_t Version = 19;
+constexpr static uint32_t Version = 20;
 
 llvm::Expected<IndexFileIn> readRIFF(llvm::StringRef Data,
                                      SymbolOrigin Origin) {