[doc] Correct link to TopsCompressor

[BaldLee]

Currently the url of "TopsCompressor Quantization Tool" in readme is https://egc.enflame-tech.com/

However, the EGC image is currently only available to enterprise users. Hopefully, there will be a direct way to obtain TopsCompressor.

[Selkh]

The open-sourcing of TopsCompressor and other toolkits is on our roadmap, though there remains a considerable journey ahead before realization.