remove unneeded explicit lifetime
remove unneeded explicit lifetime

See https://groups.google.com/forum/#!topic/python-cffi/oe7Bd6klSZM for an
explanation:

> Btw, the "cffi_explicit_lifetimes[xcb_parts] = iov_base" line here is
> not needed, because the "xcb_parts" array will anyway be dead at the
> end of the function.  You just need to ensure that "iov_base" array
> remains valid until the end of the function too; it's enough to (but
> needed to) keep it in a local variable as you do.

tych0/xcffib