Tidy publishing config (#17)

* remove custom POM location (Gradle gets confused)

* - update GitHub actions
- use new `gradle/actions/setup-gradle`
- block cancel-in-progress for publish.yml

buildSrc/src/main/kotlin/buildsrc/conventions/publishing.gradle.kts

@@ -87,10 +87,6 @@ tasks {
         val signingRequiredPredicate = provider { signing.isRequired }
         onlyIf { signingRequiredPredicate.get() }
     }
-
-    withType<GenerateMavenPom> {
-        destination = file("$projectDir/pom.xml")
-    }
 }
 
 // https://youtrack.jetbrains.com/issue/KT-46466