Do not output empty non-root packages in tests with txt

Mostly to avoid listing every internal package in
kotlin-stdlib/kotlin-reflect, as in
https://github.com/JetBrains/kotlin/blob/acd5b62148d797ffd24c4811d1d663f0c1ae7885/compiler/testData/diagnostics/testsWithUnsignedTypes/conversions/conversionOfSignedToUnsigned.txt#L144

compiler/testData/diagnostics/tests/callableReference/classVsPackage.txt

@@ -40,12 +40,6 @@ package a {
 // -- Module: <m3> --
 package
 
-package a {
-
-    package a.b {
-    }
-}
-
 package test {
     public fun test(): kotlin.reflect.KFunction1<a.b.c, kotlin.Unit>
 }