[clangd][NFC] Reserve storage when creating semantic token encoding.

[sammccall]

Thanks!

clang-tools-extra/clangd/Protocol.cpp

return llvm::json::Object{
       {"uri", FStatus.uri},
       {"state", FStatus.state},
   };
 }
 
 constexpr unsigned SemanticTokenEncodingSize = 5;
 static llvm::json::Value encodeTokens(llvm::ArrayRef<SemanticToken> Toks) {
   llvm::json::Array Result;
+  Result.reserve(SemanticTokenEncodingSize * Toks.size());
   for (const auto &Tok : Toks) {
     Result.push_back(Tok.deltaLine);
     Result.push_back(Tok.deltaStart);
     Result.push_back(Tok.length);
     Result.push_back(Tok.tokenType);
     Result.push_back(Tok.tokenModifiers);
   }
   assert(Result.size() == SemanticTokenEncodingSize * Toks.size());