[FIR] Don't render ! at the end of ConeFlexibleType

compiler/fir/analysis-tests/testData/resolve/inference/capturedTypeForJavaTypeParameter.fir.txt

@@ -4,5 +4,5 @@ FILE: main.kt
     public final fun <D : R|A|> foo(b: R|B<D>|): R|kotlin/Unit| {
     }
     public final fun main(b: R|B<*>|): R|kotlin/Unit| {
-        R|/foo|<R|ft<A, A?>!|>(R|<local>/b|)
+        R|/foo|<R|ft<A, A?>|>(R|<local>/b|)
     }

compiler/fir/analysis-tests/testData/resolve/inference/integerLiteralAsComparable.fir.txt

@@ -7,5 +7,5 @@ FILE: main.kt
     }
     public final fun main(): R|kotlin/Unit| {
         R|/K.K|<R|kotlin/Int|>(Int(0))
-        R|/JavaClass.JavaClass|<R|ft<kotlin/Int, kotlin/Int?>!|>(Int(0))
+        R|/JavaClass.JavaClass|<R|ft<kotlin/Int, kotlin/Int?>|>(Int(0))
     }