Update out-of-date documentation

We no longer can build closure-compiler with Java 8

PiperOrigin-RevId: 597316146

README.md

@@ -218,7 +218,7 @@ To build the compiler yourself, you will need the following:
 
 Prerequisite                                                               | Description
 -------------------------------------------------------------------------- | -----------
-[Java 8 or later](https://java.com)                                        | Used to compile the compiler's source code.
+[Java 11 or later](https://java.com)                                       | Used to compile the compiler's source code.
 [Git](https://git-scm.com/)                                                | Used by Bazel to download dependencies.
 [Bazelisk](https://bazel.build/install/bazelisk) | Used to build the various compiler targets.