docs: shorten run command and use published version (google-gemini#16172)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: Tommaso Sciortino <[email protected]>

Author: 3 people

README.md

@@ -39,7 +39,7 @@ Learn all about Gemini CLI in our [documentation](https://geminicli.com/docs/).
 
 ```bash
 # Using npx (no installation required)
-npx https://github.com/google-gemini/gemini-cli
+npx @google/gemini-cli
 ```
 
 #### Install globally with npm