Wrong coll at ArrayBuffer.padTo

[som-snytt]

Compiler version

3.6.4

Problem

ArrayBuffer#padTo doc does not respect its $coll definition. ("A copy of this sequence...")

https://www.scala-lang.org/files/archive/api/current/scala/collection/mutable/ArrayBuffer.html#padTo-fffffb3c

Expectation

Works as on Scala 2, where it calls itself an "array buffer".

https://www.scala-lang.org/api/2.13.15/scala/collection/mutable/ArrayBuffer.html#padTo[B%3E:A](len:Int,elem:B):CC[B]

Noticed at related ticket scala/bug#12908 (comment)

where Buffer is supplied with define coll so that it no longer calls itself "shrinkable".