MAINT: fix typo in Travis environment variable

Author: lesteve

.travis.yml

@@ -42,7 +42,7 @@ matrix:
     # It also runs tests requiring Pandas and PyAMG
     - env: DISTRIB="conda" PYTHON_VERSION="3.6.2" INSTALL_MKL="true"
            NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1" PANDAS_VERSION="0.20.3"
-           CYTHON_VERSION="0.26.1" PYAMG_VERSIONi="3.3.2" PILLOW_VERSION="4.3.0"
+           CYTHON_VERSION="0.26.1" PYAMG_VERSION="3.3.2" PILLOW_VERSION="4.3.0"
            COVERAGE=true
            CHECK_PYTEST_SOFT_DEPENDENCY="true" TEST_DOCSTRINGS="true"
       if: type != cron