MINOR: Update the README file in examples. (#12272)

Modify Intellij to IntelliJ IDEA, and mention KRaft in example docs.

Reviewers: Divij Vaidya <divijvaidya13@gmail.com>, Kvicii <kvicii.yu@gmail.com>, dengziming <dengziming1993@gmail.com>

examples/README

@@ -2,11 +2,11 @@ This directory contains examples of client code that uses kafka.
 
 To run the demo:
 
-   1. Start Zookeeper and the Kafka server
+   1. In Zookeeper mode, Start Zookeeper and the Kafka server. In KRaft mode, start the Kafka server.
    2. For unlimited sync-producer-consumer run, `run bin/java-producer-consumer-demo.sh sync`
    3. For unlimited async-producer-consumer run, `run bin/java-producer-consumer-demo.sh`
    4. For exactly once demo run, `run bin/exactly-once-demo.sh 6 3 50000`,
       this means we are starting 3 EOS instances with 6 topic partitions and 50000 pre-populated records.
    5. Some notes for exactly once demo:
       5.1. The Kafka server has to be on broker version 2.5 or higher.
-      5.2. You could also use Intellij to run the example directly by configuring parameters as "Program arguments"
+      5.2. You could also use IntelliJ IDEA to run the example directly by configuring parameters as "Program arguments"

examples/src/main/java/kafka/examples/KafkaExactlyOnceDemo.java

@@ -39,7 +39,7 @@ import java.util.concurrent.TimeUnit;
  *   - records: number of records
  * An example argument list would be `6 3 50000`.
  *
- * If you are using Intellij, the above arguments should be put in the configuration's `Program Arguments`.
+ * If you are using IntelliJ IDEA, the above arguments should be put in the configuration's `Program Arguments`.
  * Also recommended to set an output log file by `Edit Configuration -> Logs -> Save console
  * output to file` to record all the log output together.
  *