fix: rename test module to tests

examples/acceptance_tests/011/lib/tests.ak

@@ -0,0 +1,10 @@
+pub fn map(xs: List<a>, f: fn(a) -> result) -> List<result> {
+  when xs is {
+    [] -> []
+    [x, ..rest] -> [f(x), ..map(rest, f)]
+  }
+}
+
+test map_1() {
+  map([], fn(n) { n + 1 }) == []
+}