packaging: dropping builddep on otopi-devtool

We don't use otopi-bundle, so no reason for requiring it.
We can also avoid to require otopi at build time since it's
not used by the build process.
It's a runtime requirement only.

Change-Id: I0e3f21ad146c75cd2bc75f13a7bf49dcb35c6b3d
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>