Remove rules_scala prebuilt protoc toolchain

Using Bazel 9 with `protobuf` v34.0 automatically enables the prebuilt
`protoc` toolchain from `@protobuf`. There's no need to keep using the
`rules_scala` toolchain, which breaks with `protobuf` v34.0 because
`rules_scala` v7.2.4 doesn't support it. See
bazel-contrib/rules_scala#1820.

Also contains `MODULE.bazel.lock` updates generated by the
`--lockfile_mode=refresh` flag.

`bazel build //...` and `bazel test //...` both succeed. However, this
still causes a `protoc` rebuild, thanks to a `@grpc-java` dependency:

```txt
$ bazel query 'somepath(//..., @protobuf//:protoc)'

//java/com/engflow/notificationqueue/demoserver:server_java_grpc_proto
@grpc-java//compiler:java_grpc_library_toolchain
@protobuf//:protoc
```

`@grpc-java//compiler:java_grpc_library_toolchain` is a
`java_grpc_library` target. That rule's `_protoc` attribute is hardcoded
to `Label("@com_google_protobuf//:protoc")`:

- https://github.com/grpc/grpc-java/blob/v1.79.0/compiler/BUILD.bazel#L44-L49
- https://github.com/grpc/grpc-java/blob/v1.79.0/java_grpc_library.bzl#L44

Author: mbland

MODULE.bazel

@@ -45,8 +45,6 @@ http_archive(
     url = "https://github.com/abseil/abseil-py/archive/refs/tags/v2.1.0.tar.gz",
 )
 
-register_toolchains("@rules_scala_protoc_toolchains//:all")
-
 bazel_dep(name = "bazel_skylib", version = "1.9.0")
 bazel_dep(name = "engflowapis-java", version = "2025.03.14-12.58.52")
 bazel_dep(name = "platforms", version = "1.0.0")
@@ -167,11 +165,4 @@ scala_deps = use_extension(
 scala_deps.scala()
 scala_deps.scalatest()
 
-scala_protoc = use_extension(
-    "@rules_scala//scala/extensions:protoc.bzl",
-    "scala_protoc",
-    dev_dependency = True,
-)
-use_repo(scala_protoc, "rules_scala_protoc_toolchains")
-
 bazel_dep(name = "rules_shell", version = "0.6.1")