Broken generation of API documentation using scaladoc

[WojciechMazur]

The changes to versioning in the build affected the scaladoc/generateStableScala3Documentation task.
It now silently fails by not emitting index.html
The issue can be noticed in the logs of this task:

scaladoc will ignore following non-existent paths: 
  out/bootstrap/scala2-library-bootstrapped/scala-3.6.1-bin-SNAPSHOT-nonbootstrapped/classes, 
  out/bootstrap/scala3-library-bootstrapped/scala-3.6.1-bin-SNAPSHOT-nonbootstrapped/classes,
  tmp/interfaces/target/classes, 
  out/bootstrap/tasty-core-bootstrapped/scala-3.6.1-bin-SNAPSHOT-nonbootstrapped/classes

tmp/interfaces/target/classes is a hard-coded path, it should be removed as we're not emitting API for compiler-interfaces

The 3 remaining paths are incorrect in such a way that when using baseVersion = "3.6.1" the non-boostrapepd output files are present in the 3.6.1-RC1-bin-... directories instead.