FIR CFG: remove liveness analysis from lambda reassignment analyzer

Handling try/catch and break/continue is too hard here, and failing to
do that properly can create incorrect smartcast. Better be conservative
and assume all code is live.

compiler/testData/diagnostics/tests/smartCasts/variables/capturedWithControlJumps.fir.kt

@@ -50,6 +50,6 @@ fun test4() {
             return
         }
         x = null
-        lambda?.invoke()
+        lambda<!UNNECESSARY_SAFE_CALL!>?.<!>invoke()
     }
 }