[Docs] Fix required version of an example of importlib (GH-10118)

§31.5.6.3. Importing a source file directly: `module_from_spec` is new in Python 3.5.
(cherry picked from commit 16c8a53)

Co-authored-by: E Kawashima <e-kwsm@users.noreply.github.com>

Doc/library/importlib.rst

@@ -1404,7 +1404,7 @@ Importing a source file directly
 ''''''''''''''''''''''''''''''''
 
 To import a Python source file directly, use the following recipe
-(Python 3.4 and newer only)::
+(Python 3.5 and newer only)::
 
   import importlib.util
   import sys