remove Bazel 6 branch (#337)

Now that https://github.com/bazelbuild/rules_java/commit/b55339e359675d03a4f1cc001f1840d0b27966df has landed, remove Bazel 6-specific branch.

Closes #337

COPYBARA_INTEGRATE_REVIEW=https://github.com/bazelbuild/rules_java/pull/337 from benjaminp:bazel-6 f4c631a13d6e7c3bf55e29b52cc418f4b663e141
PiperOrigin-RevId: 837452933
Change-Id: I68e8171ae4e70600cc82d09af75c15726f6d7ee6

toolchains/local_java_repository.bzl

diff --git a/toolchains/local_java_repository.bzl b/toolchains/local_java_repository.bzl
index ba526a1..769c2d1 100644
--- a/toolchains/local_java_repository.bzl
+++ b/toolchains/local_java_repository.bzl
@@ -14,7 +14,6 @@
 
 """Rules for importing a local JDK."""
 
-load("@bazel_features//private:util.bzl", _bazel_version_ge = "ge")
 load("//java/toolchains:java_runtime.bzl", "java_runtime")
 load(":default_java_toolchain.bzl", "default_java_toolchain")
 
@@ -236,17 +235,10 @@
 )
 """ % (local_java_runtime_name, runtime_name, java_home, version)
 
-    if _bazel_version_ge("7.0.0"):
-        # Bazel 7+ uses @platforms//host for the host platform.
-        load_host_constraints = 'load("@platforms//host:constraints.bzl", "HOST_CONSTRAINTS")\n'
-    else:
-        # Bazel 6 uses @local_config_platform instead, but it's being removed in Bazel 9.
-        load_host_constraints = 'load("@local_config_platform//:constraints.bzl", "HOST_CONSTRAINTS")\n'
-
     repository_ctx.file(
         "BUILD.bazel",
         'load("@rules_java//toolchains:local_java_repository.bzl", "local_java_runtime")\n' +
-        load_host_constraints +
+        'load("@platforms//host:constraints.bzl", "HOST_CONSTRAINTS")\n' +
         build_file +
         local_java_runtime_macro,
     )