[FIR] Remove FirOperatorCall node from fir tree

compiler/fir/raw-fir/light-tree2fir/src/org/jetbrains/kotlin/fir/lightTree/converter/ExpressionsConverter.kt

@@ -378,14 +378,7 @@ class ExpressionsConverter(
                     explicitReceiver = getAsFirExpression(argument, "No operand")
                 }
             }
-            else -> {
-                val firOperation = operationToken.toFirOperation()
-                buildOperatorCall {
-                    source = unaryExpression.toFirSourceElement()
-                    operation = firOperation
-                    argumentList = buildUnaryArgumentList(getAsFirExpression<FirExpression>(argument, "No operand"))
-                }
-            }
+            else -> throw IllegalStateException("Unexpected expression: ${unaryExpression.asText}")
         }
     }
 

compiler/fir/raw-fir/light-tree2fir/src/org/jetbrains/kotlin/fir/lightTree/fir/WhenEntry.kt

@@ -35,7 +35,6 @@ data class WhenEntry(
 
     fun toFirWhenConditionWithoutSubject(): FirExpression {
         return when (val condition = conditions.firstOrNull()) {
-//            is FirOperatorCall -> condition.arguments.first()
             null -> buildErrorExpression(null, ConeSimpleDiagnostic("No expression in condition with expression", DiagnosticKind.Syntax))
             else -> condition
         }

compiler/fir/raw-fir/psi2fir/src/org/jetbrains/kotlin/fir/builder/RawFirBuilder.kt

@@ -1687,13 +1687,7 @@ class RawFirBuilder(
                         explicitReceiver = argument.toFirExpression("No operand")
                     }
                 }
-                else -> {
-                    buildOperatorCall {
-                        source = expression.toFirSourceElement()
-                        operation = operationToken.toFirOperation()
-                        argumentList = buildUnaryArgumentList(argument.toFirExpression("No operand"))
-                    }
-                }
+                else -> throw IllegalStateException("Unexpected expression: ${expression.text}")
             }
         }