DOC: fix some spelling issues over multiple files
This is from the output of codespell and may be backported.
diff --git a/doc/intro.txt b/doc/intro.txt
index 896a1c1..c802140 100644
--- a/doc/intro.txt
+++ b/doc/intro.txt
@@ -1276,7 +1276,7 @@
On Linux, a new starting process may communicate with the previous one to reuse
its listening file descriptors so that the listening sockets are never
-interrupted during the process' replacement.
+interrupted during the process's replacement.
3.4.3. Advanced features : Scripting