Some issues in examples

[pingyu]

Bug Report

1. Describe the bug

There are some issues in examples:

• In RawKV example here, the signature of main (public static void main()) is not correct.
• In README.md, the signature of main (public static void main()) is not correct.

2. Minimal reproduce step (Required)

N/A. Documents issue.

3. What did you see instead (Required)

N/A.

4. What did you expect to see? (Required)

N/A.

5. What are your Java Client and TiKV versions? (Required)

• Client Java: master
• TiKV: