Java: Fix documentation to reflect correct enum value for OPEN_AI. (#3114)

Fix pom.xml file to reflect correct class path for example in
sample-code README.

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### Contribution Checklist

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- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
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java/samples/sample-code/README.md

@@ -42,7 +42,7 @@ You can define the provider of Open AI (openai.com or Azure), this can be done b
 property or environment variable to either `OPENAI` or `AZURE_OPEN_AI`, i.e.:
 
 ```shell
-OPENAI_CLIENT_TYPE=OPENAI ../../mvnw exec:java -Dsample=Example04_CombineLLMPromptsAndNativeCode
+OPENAI_CLIENT_TYPE=OPEN_AI ../../mvnw exec:java -Dsample=Example04_CombineLLMPromptsAndNativeCode
 
 OR
 
@@ -64,7 +64,7 @@ You can set the location of a properties file, by setting the `CONF_PROPERTIES`
 
 ```shell
 CONF_PROPERTIES=my.properties \
-OPENAI_CLIENT_TYPE=OPENAI \
+OPENAI_CLIENT_TYPE=OPEN_AI \
 ../../mvnw exec:java -Dsample=Example04_CombineLLMPromptsAndNativeCode
 
 OR
@@ -120,8 +120,8 @@ AZURE_OPEN_AI_ENDPOINT="endpoint url" \
 ../../mvnw clean package exec:java -Dsample=Example04_CombineLLMPromptsAndNativeCode
 
 # OPENAI:
-OPENAI_CLIENT_TYPE=OPENAI \
+OPENAI_CLIENT_TYPE=OPEN_AI \
 OPEN_AI_KEY="my-key" \
 OPEN_AI_ORGANIZATION_ID="organisation id" \
 ../../mvnw clean package exec:java -Dsample=Example04_CombineLLMPromptsAndNativeCode
-```
+```

java/samples/sample-code/pom.xml

@@ -98,10 +98,10 @@
                     </execution>
                 </executions>
                 <configuration>
-                    <mainClass>com.microsoft.semantickernel.syntaxexamples.${sample}</mainClass>
+                    <mainClass>com.microsoft.semantickernel.samples.syntaxexamples.${sample}</mainClass>
                 </configuration>
             </plugin>
         </plugins>
     </build>
 
-</project>
+</project>