Allow building with GDC 10.3

tests/tanya/algorithm/tests/mutation.d

@@ -39,7 +39,11 @@ import tanya.test.stub;
         int value;
 
         void opCall(int value) @nogc nothrow pure @safe
-        in (this.value == 0)
+        in
+        {
+            assert(this.value == 0);
+        }
+        do
         {
             this.value = value;
         }

tests/tanya/range/tests/adapter.d

@@ -12,18 +12,6 @@ private struct Container
     }
 }
 
-// Broken test because of the issue #20006.
-@nogc nothrow pure @safe unittest
-{
-    auto func()()
-    {
-        Container container;
-        return backInserter(container);
-    }
-    // static assert(!is(typeof(func!())));
-    static assert(is(typeof(func!())));
-}
-
 @nogc nothrow pure @safe unittest
 {
     Container container;