Update rules_python in README to match WORKSPACE

Keeps the `README` guidance in sync with what we're actually using in
`WORKSPACE` for consistency's sake.

@crt-31 and I found that the Windows build failure for bazel-contrib#1710 mentioned
in the earlier commit is related to the Windows/MSVC file path length
limit. `src/google/protobuf/compiler/java/java_features.pb.h`, the path
specified in the error message, doesn't exist until `protobuf` v25.0.

- protocolbuffers/protobuf#12947

Furthermore, the Protobuf team currently plans to just drop MSVC
support:

- https://protobuf.dev/news/v30/#poison-msvc--bazel
- protocolbuffers/protobuf#20085

I plan to experiment again with "Protobuf Toolchainization", which I'd
tried in October when beginning the Bzlmod experiment. Here are some
interesting background resources before I dig in on that:

- bazelbuild/rules_proto#213
- bazelbuild/rules_proto#179
- https://github.com/bazelbuild/rules_proto/releases/tag/6.0.0
- https://github.com/aspect-build/toolchains_protoc/
- protocolbuffers/protobuf#20182
- protocolbuffers/protobuf#19679
- protocolbuffers/protobuf#19558

Author: mbland

README.md

@@ -74,9 +74,9 @@ bazel_skylib_workspace()
 # Otherwise you may get the version defined in the `com_google_protobuf` repo.
 http_archive(
     name = "rules_python",
-    sha256 = "9c6e26911a79fbf510a8f06d8eedb40f412023cf7fa6d1461def27116bff022c",
-    strip_prefix = "rules_python-1.1.0",
-    url = "https://github.com/bazelbuild/rules_python/releases/download/1.1.0/rules_python-1.1.0.tar.gz",
+    sha256 = "2ef40fdcd797e07f0b6abda446d1d84e2d9570d234fddf8fcd2aa262da852d1c",
+    strip_prefix = "rules_python-1.2.0",
+    url = "https://github.com/bazelbuild/rules_python/releases/download/1.2.0/rules_python-1.2.0.tar.gz",
 )
 
 load("@rules_python//python:repositories.bzl", "py_repositories")