Update README.md with license information

Hi, I'm Chen, a DevRel specialist from 01.AI.
We have updated our license from yi-license to apache-2.0, and this PR is about the update for your model.
Apache-2.0 enables more free and flexible use and distribution, promoting open collaboration and innovation.
If it looks good to you, you can update other Yi model derivatives now licensed under yi-license to apache-2.0.
Thanks for your understanding and cooperation.

README.md

@@ -1,7 +1,5 @@
 ---
-license: other
-license_name: yi-license
-license_link: LICENSE
+license: apache-2.0
 ---
 # Model Card for yi-34b-v2