AdjacentSpec BigDecimal test case failing on recent Scala 2.13 nightlies

this came up in the Scala 2.13 community build. after https://github.com/scala/community-builds/commit/54060a29041b3e4a229ff3d138df8497640e4d97 , refined started failing with:

```
```

the problem is reproducible outside dbuild just with `++2.13.1-bin-c5eed1d` (after [adding a resolver](https://stackoverflow.com/questions/40622878/how-do-i-tell-sbt-to-use-a-nightly-build-of-scala-2-12-or-2-13/40622879#40622879)) followed by `coreJVM/Test/compile`

looking at `git log --merges 63f89ba..c5eed1d`, it seems likely the cause is https://github.com/scala/scala/pull/8072

@lrytz @fthomas does this seem like a progression to you, and not a regression?

in the community build, I can work around it by temporarily excluding `AdjacentSpec.scala`