man/ocitools-generate: Reword --poststop (after container-process exit)

"is stopped" echoes the spec [1].  I'd be a bit happier if the spec
used "exits" instead of "is stopped" (to avoid confusion with
SIGSTOP), but this man page is not the place to be generating new
language.

[1]: https://github.com/opencontainers/runtime-spec/blob/v0.5.0/config.md#poststop

Signed-off-by: W. Trevor King <wking@tremily.us>

man/ocitools-generate.1.md

@@ -120,8 +120,8 @@ inside of the container.
   main process has been created.
 
 **--poststop**=CMD
-  Path to command to run in poststop hooks. This command will be run after the
-  container completes but before the container process is destroyed
+  Path to command to run in poststop hooks. The command will be run
+  after the container process is stopped.
 
 **--prestart**=CMD
   Path to command to run in prestart hooks. This command will be run before