[ci] point to latest CMake modules (#2140)

python-package/README.rst

@@ -112,7 +112,7 @@ All available options:
 
 - opencl-library
 
-For more details see `FindBoost <https://cmake.org/cmake/help/v3.8/module/FindBoost.html>`__ and `FindOpenCL <https://cmake.org/cmake/help/v3.8/module/FindOpenCL.html>`__.
+For more details see `FindBoost <https://cmake.org/cmake/help/latest/module/FindBoost.html>`__ and `FindOpenCL <https://cmake.org/cmake/help/latest/module/FindOpenCL.html>`__.
 
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