[IR] Don't render facade classes in JVM fq-names in irText tests

This makes the tests more compatible with non-JVM backends
(see KT-58605)

compiler/testData/ir/irText/expressions/signedToUnsignedConversions.kt

@@ -1,8 +1,9 @@
 // WITH_STDLIB
-// IGNORE_BACKEND: JS_IR
-// IGNORE_BACKEND: JS_IR_ES6
 // !LANGUAGE: +ImplicitSignedToUnsignedIntegerConversion
 
+// MUTE_SIGNATURE_COMPARISON_K2: JS_IR
+// ^ KT-57818
+
 // FILE: signedToUnsignedConversions_annotation.kt
 
 package kotlin.internal