simplify pyenchant requirement (#3805)

diff --git a/setup.py b/setup.py
index fcc9eda..d232e0b 100644
--- a/setup.py
+++ b/setup.py
@@ -293,7 +293,7 @@
         "test": test_requirements,
         "docstest": [
             "doc8",
-            "pyenchant != 1.6.9, != 1.6.10",
+            "pyenchant >= 1.6.11",
             "readme_renderer >= 16.0",
             "sphinx != 1.6.1, != 1.6.2, != 1.6.3",
             "sphinx_rtd_theme",