Skip doc generation for nonbootstrapped projects

fix #25704

Previously, running `sbt publishLocal` causes scaladoc generation for `scala-library-nonbootstrapped` and `scala3-library-nonbootstrapped`.

These two projects don't explicitly set `Compile / packageDoc / publishArtifact := false`, and therefore sbt defaults to generate doc jars on `publishLocal`.

However, IIUC, there's no point of generating scaladoc for nonbootstrapped projects because these artifacts are only published locally for bootstrapping (and local development), and the bootstrapped projects reference packageBin outputs and don't care about packageDoc.
In fact, other nonbootstrapped projects like `scala3-compiler-nonbootstrapped` and `tasty-core-nonbootstrapped` already set `packageDoc / publishArtifact := false`.

In my local environemnt, clean build with `publishLocal`, previously took 230s, and not it took around 90s.

Author: tanishiking

project/Build.scala

@@ -1127,6 +1127,7 @@ object Build {
       ),
       // Packaging configuration of the stdlib
       Compile / publishArtifact := true,
+      Compile / packageDoc / publishArtifact := false,
       Test    / publishArtifact := false,
       // Project specific target folder. sbt doesn't like having two projects using the same target folder
       target := target.value / "scala-library-nonbootstrapped",
@@ -1176,6 +1177,7 @@ object Build {
       emptyPublishedJarSettings,  // Validate JAR is empty (only META-INF)
       // Packaging configuration of the stdlib
       Compile / publishArtifact := true,
+      Compile / packageDoc / publishArtifact := false,
       Test    / publishArtifact := false,
       // Project specific target folder. sbt doesn't like having two projects using the same target folder
       target := target.value / "scala3-library-nonbootstrapped",