Revert "Add selectors34 fallback for py27 under 64-bit Win"

This reverts commit e996f20.

Thanks to @sethmlarson who published `selectors==2.0.2` on PyPI
we no longer need a fallback to `selectors34`.

Ref: https://twitter.com/sethmlarson/status/1285706586514751489

cheroot/_compat.py

@@ -12,10 +12,7 @@
 try:
     import selectors  # lgtm [py/unused-import]
 except ImportError:
-    try:
-        import selectors2 as selectors  # noqa: F401  # lgtm [py/unused-import]
-    except ImportError:
-        import selectors34 as selectors  # noqa: F401 # lgtm [py/unused-import]
+    import selectors2 as selectors  # noqa: F401  # lgtm [py/unused-import]
 
 try:
     import ssl

setup.cfg

@@ -65,8 +65,7 @@ setup_requires =
 # These are required in actual runtime:
 install_requires =
     backports.functools_lru_cache; python_version < '3.3'
-    selectors2; python_version < '3.4' and (sys_platform != "win32" or (sys_platform == "win32" and python_version >= '3.0'))
-    selectors34; python_version < '3.0' and sys_platform == "win32"
+    selectors2; python_version< '3.4'
     six>=1.11.0
     more_itertools>=2.6
     jaraco.functools