Update App Engine Java runtime entrypoint examples in README.

PiperOrigin-RevId: 915517031
Change-Id: I63419f58824813712eb5c754058e5b62a024ddc4

Author: ludoch

README.md

@@ -319,11 +319,16 @@ The Java 17, Java 21 and 25 runtimes can benefit from extra user configuration w
 The default entrypoint used to boot the JVM is generated by App Engine Buildpacks.
 Essentially, it is equivalent to define this entrypoint in the `appengine-web.xml` file. For example:
 
-<pre><entrypoint>java --add-opens java.base/java.lang=ALL-UNNAMED  --add-opens java.base/java.nio.charset=ALL-UNNAMED -showversion -Xms32M -Xmx204M -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:+PrintCommandLineFlags -Dclasspath.runtimebase=/base/java_runtime -Djava.class.path=/base/java_runtime/runtime-main.jar -Djava.library.path=/base/java_runtime: com/google/apphosting/runtime/JavaRuntimeMainWithDefaults --fixed_application_path=/workspace /base/java_runtime</entrypoint></pre>
+<pre style="white-space: pre-wrap; word-wrap: break-word;"><entrypoint>java --add-opens java.base/java.lang=ALL-UNNAMED --add-opens java.base/java.nio.charset=ALL-UNNAMED --add-opens java.base/java.util.concurrent=ALL-UNNAMED --add-opens java.logging/java.util.logging=ALL-UNNAMED -showversion -Xms32M -Xmx204M -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:+PrintCommandLineFlags -Dclasspath.runtimebase=/base/java_runtime -Djava.class.path=/base/java_runtime/runtime-main.jar -Djava.library.path=/base/java_runtime: com.google.apphosting.runtime.JavaRuntimeMainWithDefaults --fixed_application_path=/workspace /base/java_runtime</entrypoint></pre>
+
+
+For Java25, the base layer is in the builder image under `/layers/google.java.appengine/java_runtime`, so:
+
+<pre style="white-space: pre-wrap; word-wrap: break-word;"><entrypoint>java --add-opens java.base/java.lang=ALL-UNNAMED --add-opens java.base/java.nio.charset=ALL-UNNAMED --add-opens java.base/java.util.concurrent=ALL-UNNAMED --add-opens java.logging/java.util.logging=ALL-UNNAMED -showversion -Xms32M -Xmx204M -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:+PrintCommandLineFlags -Dclasspath.runtimebase=/layers/google.java.appengine/java_runtime -Djava.class.path=/layers/google.java.appengine/java_runtime/runtime-main.jar -Djava.library.path=/layers/google.java.appengine/java_runtime: com.google.apphosting.runtime.JavaRuntimeMainWithDefaults --fixed_application_path=/workspace /layers/google.java.appengine/java_runtime</entrypoint></pre>
 
 We do not recommend changing this default entrypoint as the memory settings are calculated based on the instance type (F1, F2, F4) and memory available.
 
-By default, we use `--add-opens java.base/java.lang=ALL-UNNAMED  --add-opens java.base/java.nio.charset=ALL-UNNAMED` to open some necessary JDK APIs.
+By default, we use `--add-opens java.base/java.lang=ALL-UNNAMED --add-opens java.base/java.nio.charset=ALL-UNNAMED --add-opens java.base/java.util.concurrent=ALL-UNNAMED` to open some necessary JDK APIs.
 
 
 ## Entry Point Features