docs: Use correct pip extension path in generated release notes (#1310)

Also add a note that bzlmod support is still beta.

.github/workflows/create_archive_and_notes.sh

diff --git a/.github/workflows/create_archive_and_notes.sh b/.github/workflows/create_archive_and_notes.sh
index 02279bc..f7a291a 100755
--- a/.github/workflows/create_archive_and_notes.sh
+++ b/.github/workflows/create_archive_and_notes.sh
@@ -27,12 +27,14 @@
 cat > release_notes.txt << EOF
 ## Using Bzlmod with Bazel 6
 
+**NOTE: bzlmod support is still beta. APIs subject to change.**
+
 Add to your \`MODULE.bazel\` file:
 
 \`\`\`starlark
 bazel_dep(name = "rules_python", version = "${TAG}")
 
-pip = use_extension("@rules_python//python:extensions.bzl", "pip")
+pip = use_extension("@rules_python//python/extensions:pip.bzl", "pip")
 
 pip.parse(
     name = "pip",