Remove compatibility_level from MODULE files. (#1063)

Starting in Bazel 8, this value is unused.
Starting in Bazel 9, this print a warning that the value is unused.
In Bazel 10, setting it will become a failure.

MODULE.bazel

diff --git a/MODULE.bazel b/MODULE.bazel
index 2c7fef4..f47565f 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -1,7 +1,6 @@
 module(
     name = "rules_pkg",
     version = "",  # set by release pipeline from version.bzl.
-    compatibility_level = 1,
     repo_name = "rules_pkg",
 )
 

providers/MODULE.bazel

diff --git a/providers/MODULE.bazel b/providers/MODULE.bazel
index fa4467d..753c356 100644
--- a/providers/MODULE.bazel
+++ b/providers/MODULE.bazel
@@ -1,7 +1,6 @@
 module(
     name = "rules_pkg_providers",
     version = "",  # set by release pipeline from version.bzl.
-    compatibility_level = 1,
     repo_name = "rules_pkg_providers",
 )
 

tests/mappings/external_repo/MODULE.bazel

diff --git a/tests/mappings/external_repo/MODULE.bazel b/tests/mappings/external_repo/MODULE.bazel
index 0137c38..0dca2e8 100644
--- a/tests/mappings/external_repo/MODULE.bazel
+++ b/tests/mappings/external_repo/MODULE.bazel
@@ -15,7 +15,6 @@
 module(
     name = "test_external_project",
     version = "0",
-    compatibility_level = 0,
 )
 
 local_path_override(