Update platforms dependency.

Signed-off-by: Henner Zeller <hzeller@google.com>

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index b09f480..8cea500 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -6,9 +6,11 @@
 # Bazel platform rules, needed as dependency to absl.
 http_archive(
     name = "platforms",
-    sha256 = "a879ea428c6d56ab0ec18224f976515948822451473a80d06c2e50af0bbe5121",
-    strip_prefix = "platforms-da5541f26b7de1dc8e04c075c99df5351742a4a2",
-    urls = ["https://github.com/bazelbuild/platforms/archive/da5541f26b7de1dc8e04c075c99df5351742a4a2.zip"],  # 2022-05-27
+    urls = [
+        "https://mirror.bazel.build/github.com/bazelbuild/platforms/releases/download/0.0.6/platforms-0.0.6.tar.gz",
+        "https://github.com/bazelbuild/platforms/releases/download/0.0.6/platforms-0.0.6.tar.gz",
+    ],
+    sha256 = "5308fc1d8865406a49427ba24a9ab53087f17f5266a7aabbfc28823f3916e1ca",
 )
 
 http_archive(