Bump MODULE.bazel version to 7.1.6 (#1800)

Also updates `usagesDigest` in a couple of test repo `MODULE.bazel.lock`
files.

---

This is minor housekeeping before publishing the v7.1.6 release.

We may consider whether it's worth continuing to update the version
number like this or using a different schema. The Bazel Central Registry
will always update the published `MODULE.bazel` file to contain the
correct version number. See:

- https://github.com/bazel-contrib/publish-to-bcr/blob/v1.0.0/src/domain/create-entry.ts#L176-L216

Author: mbland

MODULE.bazel

@@ -2,7 +2,7 @@
 
 module(
     name = "rules_scala",
-    version = "7.1.5",
+    version = "7.1.6",
     bazel_compatibility = [">=7.1.0"],
     compatibility_level = 7,
 )