Do not render declarations from other modules in diagnostic tests

Because PackageViewDescriptor may consist of several package fragments from
different modules (see LazyPackageViewDescriptorImpl#fragments), we now filter
out fragments from irrelevant modules before rendering them into the .txt

compiler/testData/diagnostics/tests/smartCasts/publicVals/otherModule.txt

@@ -18,10 +18,6 @@ package
 
 package a {
     public fun a.X.gav(): kotlin.Int
-
-    public final class X {
-        // -- Module: <m1> --
-    }
 }
 
 package b {