hark-graph-hook: fix muting on %remove-graph
hark-graph-hook: fix muting on %remove-graph

*_watching was bunting to watching (i.e. a no-op), causing watching to
be wiped everytimne a graph was removed

urbit/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,urbit/urbit