[docs] Missing change documentation

[Christopher Schmitt]

Hello,

Just found a missing "changed in version" text....

while the "os" lib has a "Changed in version 3.6: Accepts a path-like
object." Text.
This is totally missing in the shutil lib. (okay you could use the argument
that shutil is using os lib and links to it but in the first moment it
totally confused me why my script wasn't working on 3.5)

Greetings,
Christopher Schmitt
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