inspiral.py: fix some ilwdchar cruft

- when writing triggers directly to sqlite databases, at one step in the process the process ID is potentially remapped and so must be re-retrieved from the output document.  this step includes a typecast to an ilwdchar object, which is now incorrect since all IDs are plain integers.  this patch removes the typecast and the import of the module it required (which no longer exists in the current production release of python-ligo-lw, which is how this was discovered)