build(gradle): replace SelfResolvingDependency by ExternalModuleDependency

`SelfResolvingDependency` was removed in Gradle 9. The original POM
filter in `publish.gradle` excluded file-based dependencies by negating
instanceof `SelfResolvingDependency`, which `FileCollectionDependency`
implemented in Gradle 8.
This change replaces it with a positive check for `ProjectDependency`
and `ExternalModuleDependency`, which are the two types that actually
have Maven coordinates and belong in a published POM.

Author: bric3

gradle/publish.gradle

@@ -38,7 +38,7 @@ publishing {
               def dependenciesNode = xml.asNode().appendNode('dependencies')
 
               project.configurations.api.allDependencies.each {
-                if ((it instanceof ProjectDependency) || !(it instanceof SelfResolvingDependency)) {
+                if (it instanceof ProjectDependency || it instanceof ExternalModuleDependency) {
                   def dependencyNode = dependenciesNode.appendNode('dependency')
                   dependencyNode.appendNode('groupId', it.group)
                   dependencyNode.appendNode('artifactId', it.name)