Update README.md with version fix

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

Author: gtinneyprophecy

README.md

@@ -150,7 +150,7 @@ MCP for Unity connects your tools using two components:
 
 **Need a fixed version?** Use a tagged URL instead (updates require uninstalling and re-installing):
 ```
-https://github.com/prophecygamestudio/unity-mcp.git?path=/MCPForUnity#v8.0.0
+https://github.com/prophecygamestudio/unity-mcp.git?path=/MCPForUnity#v8.1.6
 ```
 
 #### To install via OpenUPM