Sema: Refactor inferFromRelational()'s updating of AdjacentVars
This was all wrong.
If we have something like
($T0, $T1) conv $T2
Nothing about $T0 can influence $T1 or vice versa, but we would
put $T0 in $T1's AdjacentVars list and vice versa anyway.
On the other hand, if we have
$T0.A conv Array<$T1>
Then $T0 should appear in $T1's AdjacentVars, but it didn't.
