A small error about C++ compilation paths on cpp/README.md

[mocusez]

Describe the bug, including details regarding any error messages, version, and platform.

GraphAr is great, but when I looked at the C++ compilation documentation I found the entry path was wrong :

after git clone, it should be incubator-graphar/cpp instead of graphar/cpp

https://github.com/apache/incubator-graphar/blob/main/cpp/README.md?plain=1#L69

I convenience this is a bug due to docs/libraries/java/java.md 😂

Component(s)

C++, Documentation