fix link in README

[zhyncs]

Motivation

• fix typo
• We will directly implement and tune group GEMM using CUTLASS in sgl-kernel. cc @ispobock

Modifications

Checklist

• Format your code according to the Code Formatting with Pre-Commit.
• Add unit tests as outlined in the Running Unit Tests.
• Update documentation / docstrings / example tutorials as needed, according to Writing Documentation.
• Provide throughput / latency benchmark results and accuracy evaluation results as needed, according to Benchmark and Profiling.