Check also drop-box content in multi-module line marker tests

Related to KT-26957

idea/testData/multiModuleLineMarker/actualEnumEntriesInOneLine/jvm/jvm.kt

@@ -1,3 +1,10 @@
 package test
 
-actual enum class <lineMarker>Enum</lineMarker> { A, B, C }
+actual enum class <lineMarker descr="Has declaration in common module">Enum</lineMarker> { A, B, C }
+
+/*
+LINEMARKER: Has declaration in common module
+TARGETS:
+common.kt
+expect enum class <4>Enum { <1>A, <2>B, <3>C }
+*/