Fixed #19738 -- remove sqlite timezone adapter for IPython shell

https://code.djangoproject.com/ticket/19738

Because IPython was using naive timezone datetimes with sqlite
the adapter registered by Python would throw runtime warnings.

@aaugustin what are the implications for any raw sql running from this context - is a more clearly worded warning worth printing at the start of the session? Something like

"Raw SQL use of datetimes for sqlite will not receive Django timezone patching in this shell"