FIR DFA: don't erase statements when entering non-call-in-place lambda

Instead, rely on the variable assignment analyzer to properly restrict
smart casts. This makes error messages more consistent, but otherwise
should have no effect.

compiler/testData/diagnostics/tests/smartCasts/varnotnull/capturedInClosureModifiedBefore.fir.kt

@@ -30,7 +30,7 @@ fun baz(s: String?) {
             <!SMARTCAST_IMPOSSIBLE!>x<!>.hashCode()
         }
         run {
-            x<!UNSAFE_CALL!>.<!>hashCode()
+            <!SMARTCAST_IMPOSSIBLE!>x<!>.hashCode()
             x = null
         }
     }
@@ -40,7 +40,7 @@ fun gaz(s: String?) {
     var x = s
     if (x != null) {
         run {
-            x<!UNSAFE_CALL!>.<!>hashCode()
+            <!SMARTCAST_IMPOSSIBLE!>x<!>.hashCode()
             x = null
         }
         run {