Disable.symbols should disable both explicits and synthetics

[olafurpg]

Originally reported in scalacenter/scalafix#703

I'm trying to construct rules to Disable calls to apply on the stdlib collections, e.g.

val thing = List("foo")
thing(0)

but these only show up under synthetics in the semanticdb and I have to use these synthetic rules instead...

   "scala.collection.MapLike#apply(K)."
   "scala.collection.LinearSeqOptimized#apply(Int)."

Is this a bug or is there an explanation for it?

I expected to be able to ban them from Disable.symbols.