Fix linting issues

Author: ahejlsberg

src/compiler/checker.ts

@@ -17019,7 +17019,7 @@ namespace ts {
                 }
                 else if (flags & FlowFlags.BranchLabel) {
                     // A branching point is reachable if any branch is reachable.
-                    return some((<FlowLabel>flow).antecedents!, isReachableFlowNode);
+                    return some((<FlowLabel>flow).antecedents, isReachableFlowNode);
                 }
                 else if (flags & FlowFlags.LoopLabel) {
                     // A loop is reachable if the control flow path that leads to the top is reachable.
@@ -17331,7 +17331,7 @@ namespace ts {
             }
 
             function getTypeAtSwitchClause(flow: FlowSwitchClause): FlowType {
-                if (flow.clauseStart === flow.clauseEnd && isExhaustiveSwitchStatement((<FlowSwitchClause>flow).switchStatement)) {
+                if (flow.clauseStart === flow.clauseEnd && isExhaustiveSwitchStatement(flow.switchStatement)) {
                     return neverType;
                 }
                 const expr = flow.switchStatement.expression;