Bump minimum Java version to 17 and add Java 21 build

Change-Id: Ia063d5de28cd69152286a3dec4a6f614f1549915

tools/BUILD

diff --git a/tools/BUILD b/tools/BUILD
index 50c0463..8ea3629 100644
--- a/tools/BUILD
+++ b/tools/BUILD
@@ -5,17 +5,8 @@
 load("@rules_java//java:defs.bzl", "java_package_configuration")
 
 default_java_toolchain(
-    name = "error_prone_warnings_toolchain_java11",
-    package_configuration = [
-        ":error_prone",
-    ],
-    source_version = "11",
-    target_version = "11",
-    visibility = ["//visibility:public"],
-)
-
-default_java_toolchain(
     name = "error_prone_warnings_toolchain_java17",
+
     configuration = dict(),
     java_runtime = "@bazel_tools//tools/jdk:remotejdk_17",
     package_configuration = [
@@ -26,6 +17,19 @@
     visibility = ["//visibility:public"],
 )
 
+default_java_toolchain(
+    name = "error_prone_warnings_toolchain_java21",
+
+    configuration = dict(),
+    java_runtime = "@bazel_tools//tools/jdk:remotejdk_21",
+    package_configuration = [
+        ":error_prone",
+    ],
+    source_version = "21",
+    target_version = "21",
+    visibility = ["//visibility:public"],
+)
+
 # Error Prone errors enabled by default; see ../.bazelrc for how this is
 # enabled. This warnings list is originally based on:
 # https://github.com/bazelbuild/BUILD_file_generator/blob/master/tools/bazel_defs/java.bzl