fix: rename test module to tests

examples/acceptance_tests/002/lib/tests.ak

@@ -0,0 +1,11 @@
+pub fn repeat(x: a, n: Int) -> List<a> {
+  if n <= 0 {
+    []
+  } else {
+    [x, ..repeat(x, n - 1)]
+  }
+}
+
+test repeat_1() {
+  repeat("aiken", 2) == ["aiken", "aiken"]
+}