fix incorrect overload error in different namespaces with same suffix

===
namespace a {
    fun f() = 1
}

namespace b {
    namespace a {
        fun f() = 1
    }
}
===

compiler/testData/checkerWithErrorTypes/quick/ConflictingOverloads.jet

@@ -40,3 +40,9 @@ namespace ns2 {
     fun e() = 1
 }
 
+namespace ns3 {
+    namespace ns1 {
+        fun e() = 1
+    }
+}
+