Update the location of the required Java version after bf4b13b.

(And link to it for good measure.)

PiperOrigin-RevId: 955328807

Author: cpovirk

README.md

@@ -19,8 +19,10 @@ java -jar /path/to/google-java-format-${GJF_VERSION?}-all-deps.jar <options> [fi
 Note that it uses the `jdk.compiler` module to parse the Java source code. The
 `java` binary version used must therefore be from a JDK (not JRE) with a version
 equal to or newer than the Java language version of the files being formatted.
-The minimum Java version can be found in `core/pom.xml` (currently Java 21). An
-alternative is to use the available GraalVM based native binaries instead.
+The minimum Java version can be found in
+[`pom.xml`](https://github.com/google/google-java-format/blob/master/pom.xml)
+(currently Java 21). An alternative is to use the available GraalVM based native
+binaries instead.
 
 The formatter can act on whole files, on limited lines (`--lines`), on specific
 offsets (`--offset`), passing through to standard-out (default) or altered