haskellPackages.attoparsec-isotropic: skip problematic t_iter test

Seems like the test suite is copied from attoparsec and suffers from the
same flaws.

pkgs/development/haskell-modules/configuration-common.nix

@@ -468,6 +468,12 @@ with haskellLib;
       "$0!=\"tests.buf.t_iter\""
     ];
   }) super.attoparsec;
+  attoparsec-isotropic = overrideCabal (drv: {
+    testFlags = drv.testFlags or [ ] ++ [
+      "-p"
+      "$0!=\"tests.leftToRight.buf.t_iter\""
+    ];
+  }) super.attoparsec-isotropic;
 
   # These packages (and their reverse deps) cannot be built with profiling enabled.
   ghc-heap-view = lib.pipe super.ghc-heap-view [