doc: remove unused Russian translation files

Even though index, guide and quick start documentation pages have
Russian translation. it isn't published on readthedocs [1]. Since we
don't plan to have a Russian connector documentation for now, this patch
removes the files.

1. https://tarantool-python.readthedocs.io/en/latest/

Part of #67

Author: DifferentialOrange

Diff for: doc/guide.en.rst renamed to doc/guide.rst

@@ -27,8 +27,8 @@ Documentation
 .. toctree::
    :maxdepth: 1
 
-   quick-start.en
-   guide.en
+   quick-start
+   guide
 
 .. seealso:: `Tarantool documentation`_