change(poetry): use kevr@upgrade-starlette-0.17.0 as fastapi source

Starlette 0.16.0 has a pretty bad bug in terms of logging which
has been fixed in the 0.17.0 release. That being said, FastAPI has
not yet merged a request at tiangolo/fastapi#4145
which resolves this dependency resolution so we can use the updated
starlette package.

kevr has forked the pull request in question and we are using it
for now in our poetry dependencies to get ahead of the game.

When FastAPI upstream is updated to support 0.17.0, we'll need
to switch this back to using upstream's source.

Signed-off-by: Kevin Morris <kevr@0cost.org>